The invasion of Oahu, December 1941.

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glenn239
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(16) Naval bombardment of Oahu

Post by glenn239 » 17 May 2007 16:29

All installations on Oahu, as well as ships in the harbor, were within gunfire range of ships cruising off the coast in deep water. The potential for a naval bombardment had long been recognized by American officials, leading to the construction of a large network of coastal artillery emplacements as a precaution against it. These batteries ranged from light beach defense guns all the way up to four 16" monsters capable of hurling a shell 46,000 yards. The network was supported by observation posts scattered around the island, allowing instant feedback on spotting and providing fire control to plotting centers.

The general procedure sketched out for an IJN bombardment of Oahu are drawn from the USMC Landing Operations Doctrine, Chapter V - Naval Gunfire, 1938. It is assumed that if faced with the task, the IJN would have employed similiar tactics

http://www.ibiblio.org/hyperwar/USN/ref ... ous-5.html

The initial purpose of a bombardment of Oahu would be to eliminate the ability of the island's major bases to project air or naval power. The list of potential targets of such an attack would be the United States Navy itself, the large air stations, the naval base, the oil tanks, power generation stations, communications centers and supply dumps. Different guns were better at attacking different targets. Smaller guns were good for precision fire and support work. The large battleship guns were more appropriate for area attacks, as would be the case if striking the navy yard or an airbase,

Battleships.--These must be generally classified as deep support ships, particularly suited for participating in the preparation and for the execution of special missions* beyond the power of the other ships. If, however, hydrographic conditions permit, and there is no danger of the battleship being caught in restricted waters, these ships are ideal for furnishing close supporting fires with their 5-inch batteries


* - Special missions are defined by USMC doctrine as:

Special missions.--The larger caliber guns (8" and above) possess rates of fire too slow and their patterns are too large to make them excellent close support weapons. These large caliber guns are classified tactically as deep support weapons employed on special missions against long range targets as cities, airfields, and major fortifications, and for the destruction of heavy, permanent fortifications. The 8" guns, in the event that 6" guns are not available, can be utilized in long range counterbattery.

The tactical plan to bombard Oahu evolves from the location of the installations to be attacked, the positions of the defending coastal batteries, the depth of the waters around the island, and the maximum range of the Japanese 14", 16" and 18.1" guns firing HE and AA projectiles. The sum of these considerations makes the most efficient direction for an attack roughly southwest of Pearl Harbor, from the deeps waters beyond Barber's Point. The following gives an idea of the range from which a task might be accomplished:

Close support fire: 1,000-10,000 yards.
Indirect spotted fire vs large bases: 20,000-40,000 yards.
Indirect spotted fire vs ships in port: 16,000-24,000 yards.
Indirect spotted fire vs ships in port (elite units): 30,000 yards.


Protecting Oahu against attack relied upon an interlocking system of defenses for success. The fleet, sitting in harbor, provided the vast majority of the anti-aircraft defenses available to the island. These were of a scale such that Kido Butai could not conduct sustained attacks against the navy yard over a period of days without suffering heavy losses.

But the United States fleet could only sit in harbor if no enemy fleet came up to Oahu and destroyed it at pierside. The things that prevented this were the aircraft at Hawaii, the coastal defenses designed to ward off such assaults, and any fire the ships themselves could muster (USN ships were not netted into the coastal defense network, and therefore would have to rely upon their own spotter aircraft). On paper, the coastal defenses looked impressive. But in fact there were only two positions of four guns in total capable of contesting a serious massed attack by battleships and heavy cruisers. These were Battery Hatch and Battery Williston, situated southwest of the harbor, each being open-air 16" guns capable of hurling battleship-killing shells 20 miles out to sea.

If these two coastal batteries were silenced, then IJN fleet could approach closely enough to attack targets in the harbor with indirect fire. If the USN were still in harbor when this happened, then it risked immediate wholesale annihilation. But if the USN instead went to sea to avoid an attack, then Oahu no longer had adequate anti-aircraft defenses to protect itself, and Kido Butai could then do tremendous damage at very little cost.

Tinkerbell proposes that the solution to the problem was combined arms - IJN airpower destroys the 16" coastal guns and sweeps aside any defending ships at sea, operating outside the protective cocoon of massed A.A. in the harbor. IJN heavy surface ships then would approach and clear the port of US ships, which would remove the majority of A.A. defenses and allowing Kido Butai and the surface fleet to destroy Oahu's capability to project air and naval power. To achieve success, significant casualties amongst attacking surface ships was acceptable.

The purpose of a naval bombardment of Oahu would be:

1) To destroy the United States Pacific Fleet in port (the silencing of Williston and Hatch would probably be a prerequisite for such an attack).
2) To conduct saturation bombardments of various targets. (The IJN could perform this mission with the US Army 16" guns operational).

Long range and short range bombardment of Oahu

Image

Method.

Due to the vulnerability of spotter aircraft to defending fighters, the Main Body could not begin an attack without friendly fighters exercising control of the air. Thus a primary prerequisite to a bombardment would be to secure the air superiority necessary to allow the Main Body to approach Oahu. The weather also had to be favorable; a bombardment required good visibility to correct fall of shot. Defending USN vessels at sea would have to be driven away or sunk. Failure to meet these conditions would postpone an attack until whatever difficulty was rectified. Whether targeting ships in the harbor or bases on the island, the organizational element around which an attack is built is the fire group - a number of ships and escorts all tasked to hit targets in a similiar area of the harbor or island,

Firing runs are planned by the fire-support groups within the limits of the respective fire-support areas. The bearing of the firing runs in relation to the line of fire should be such that all the guns of the battery or batteries concerned can bear, and that the range and deflection to the target or targets engaged on the run will change as little as possible during the period of adjustment and fire for effect. The turns at the ends of the run must be made at such times that they do not interfere with the delivery of fires scheduled for specific times nor interrupt the execution of fire on a target of opportunity. >From the standpoint of effective delivery of fire the ideal firing run is on a straight course of maximum length and at minimum speed with the center of the target area bearing on the beam at the center of the run.

Range where commencement of fire would occur would depend upon the target being attacked. For ships in port, not more than 20,000 yards might be optimal. For the the large bases where accuracy wasn't paramount, it would be near the maximum available with the munitions at hand (the large bases were in the order of 50-100 times bigger than a single battleship). IJN training routinely planned for first shots at about the largest ranges possible,

"...by the mid-1930's the Japanese had sufficient confidence in their guns and gunnery that their main force units would outrange those of the US battle fleet by 4,000 to 5,000 meters. With the firepower that the Japanese navy planned to have available, the Naval Staff College estimated that the Japanese could begin to track the enemy at 40,000 meters (21.5 miles) and could...open fire at around 34,000 meters..."

Kaigun, strategy, tactics and technology in the Imperial Japanese Navy, pp262


If making a base attack, each battleship and cruiser would be responsible for attacking an individual installation (ie, Hickam). If attacking ships in port, each fire group would be assigned different areas of the harbor,

"Target areas.--Each fire-support group is assigned a definite land area within which all fires normally to be expected from the group are located."

Certain ships (Nagato, Mutsu, light cruisers, destroyers, plus all secondary batteries without a primary bombardment target) would presumably be responsible for any necessary coastal battery suppression. The method of attack in most cases would be via indirect fire from long range,

Indirect fire.--Indirect fires are fires delivered on targets which cannot be seen from the ship. These fires are spotted by plane spotters or by spotters on shore... The use of indirect fire implies that the target is not visible to the firing ship. However, these fires will usually be observed and adjusted either by air spot or by Shore Fire Control Party spotters

No shore spotters would be available, therefore all gunfire would be directed by aircraft,

Air observers.--Air observers are used primarily to control the deep support batteries of cruisers and battleships in the execution of long range fires. Normally, the ship concerned will supply the plane. The spotter may be a specially trained artillery officer of the landing force. The above arrangement reduces the chances of misunderstandings to a minimum.

IJN battleships and cruisers were capable of performing such a mission because their crews trained extensively to engage enemy ships with indirect fire at ultra-long ranges,

"Another important method of obtaining greater effective gunnery range was through the use of naval aircraft, principally floatplanes carried aboard battleships and cruiser as spotters to mark the fall of shells, thus achieving observational heights not attainable from the mast of any warship...after 1935 the navy could achieve a high rate of hits, using this method, at ranges of over 30,000 meters. The navy practiced this tactical innovation repeatedly in succeeding years, and it was incorporated into Japanese planning for the decisive gunnery duel."

Kaigun, pp260


The technique quoted from Kaigun was practiced exclusively at sea for a decisive naval battle. But the IJN could have adapted to the requirements of a base bombardment fairly easily because the methods employed in their training were identical to those necessary to attack Oahu,

Spotting.--The technique of spotting naval gunfire on shore targets by ship observers is in every respect similar to that employed in spotting fire against waterborne targets, except that the effect of slope must be taken into consideration when making range changes. The technique of spotting by air observers and by Shore Fire Control Party spotters is laid down in the Shore Fire Control Code

Offshore, attacking fire groups would be assigned to bombardment zones according to the location and inclination of their assigned targets. All ships in the same bombardment zone maintain a single line ahead formation, with all fire groups maintaining the same heading and performing turns at the same time. This technique, like all aspects of a bombardment, would require additional pre-war training,

The range to the center of the target is determined by measuring a line joining the ship's position (fixed by continuous navigational plot) and the point designated as the center of the target by the observer (either by coordinates or by reference to a plotted concentration). It is for this reason that a standard map or chart on which has been superimposed the standard grid, and which includes the fire support areas, should be furnished to all firing ships. To the range thus determined is added the position correction necessary because of the altitude of the target. The true bearing of the target is determined and the guns are laid with an appropriate deflection.

Adjustment is accomplished as for direct fire except that full battery salvos are normally used. After each ranging salvo, fire is suspended until the spot is received and applied.

When adjustment is complete and the spotter requests fire for effect, neutralizing fire is delivered as in the engagement of targets by direct fire. If the target has not been sufficiently covered in area or in density, the spotter will transmit an appropriate spot (if necessary), and request that fire for effect be repeated.

Once ranged, each battleship would saturate their target with heavy shells over the course of about 1 to 1.5 hours*.

(* - the Yamato class had a special limitation. She carried 360 rounds in ready store, with another 540 below. It was anticipated that the 360 ready rounds would be replenished from the deeper store rooms between engagements. It was possible to supply the guns from the lower shell rooms during a battle, therefore I allocate Yamato to supply a total of 720 shells in two separate attacks.)


Effect of bombardment.

This site has a pretty good interactive map of Pearl Harbor

http://plasma.nationalgeographic.com/pe ... meset.html


It is assumed that the United States Navy would never have accepted battle while in port. If it did, then the Japanese fleet should have been able to inflict tremendous damage upon it, for it was possible for Japanese ships to come as close as 20,000 yards to the anchorage and still remain outside the range of all but a few of the defending coastal batteries (and of these, none were fortified or camouflaged against air attack).

Barring incredible incompetence, a bombardment of Oahu therefore would probably occur after the USN had moved to sea and been driven from the area by air and/or sea attacks. The effect of a bombardment against land targets is an expression of the total weight of ordnance falling onto each vs. the resistance of the target to the effects of the shells. The size of the targets (airfields, ship yards, oil tank farms) were large enough that in most cases they exceeded the inherent error within the salvo patterns of attacking ships, meaning that most shells fired could be expected to hit the target. How little or how much infrastructure survived such a pounding was dependent on the number, reliability, type and power of the shells fired, and the pure random chance of where each fell within each base's area. Shell classifications were, in order of suppressive effect against exposed troops;
Antiaircraft (air burst).
High capacity (superquick fuze).
Antiaircraft (impact burst).
High capacity (short delay fuze).
Common.
Armor piercing.


To which the IJN would add at some point during 1941 or 1942 another type: The Type III incendiary shell which deposited submunitions projecting a 3000 degree Celsius flame about 15 feet for 5 seconds. Type III incendiaries commenced development in 1938 and entered service in 1942. Presumably, if quantities were issued to the fleet in time, these would not amount to much more than a few dozen shells per ship at most. Still, even in limited quantities their impact on Oahu (post-war USN sniffyness at the concept notwithstanding) would have been quite serious (see below).

Each target on Oahu will be classified by its size and suitability to attack by various types of shells. Type III, HE and AA shells would be better than AP at most jobs not involving concrete surfaces or battleship armor,

The ratio, weight of metal to weight of high explosive, generally fixes the type of fragmentation obtained. When the ratio is small, good fragmentation is obtained and the fragments are effective at greater distances. This is the type of shell used against personnel. When the ratio is large, the fragments produced are few and are effective over an area of smaller radius. This is the type of shell used against material since its heavy walls enable it to defeat the walls of the object hit and introduce the high explosive inside of the object.


The targets for bombardment:

1) Airfields.

"Airfields" are defined in area as the zones of infrastructure, not the airbase including all runways and parks. There are several measurements for effect of shells against airfields. First is their effect on buildings, supplies and equipment. Next, the destruction of the runways and parkways themselves. Finally, the damage/destruction of aircraft caught on the ground. Each shell's effective radius was different depending on which of these objectives it was used for. It was easiest of all to damage parked aircraft, after that buildings and equipment, and finally the runways themselves. As the job got harder, the effective radius of each shell diminished.

2) Oil storage tanks.

Four fields required attack. In Tinkerbell, surface vessels initially attack the oil tanks, with the Strike Force responsible for follow-up strikes against any tanks which escape destruction.

A) Tank Field 1, by Naval Hospital. 156,000 yards sq.
B) Tank Field 2, east of CINPAC HQ. 156,000 yards sq.
C) Tank Field 3, south of CINPAC HQ. 74,000 yards sq.
D) Tank Field 4, on south side of Ford Island. 105,000 yards sq.

3) Navy Yard, Submarine base and Cinpac HQ.
4) Battleships trapped in port or drydock.
5) Schofield Barracks


The IJN must reserve a large portion of heavy shells for a potential naval engagement (or port attack if the USN remained in Pearl Harbor). Tinkerbell calls for most vessels to use only 25% of their heavy caliber ammunition for the bombardment. The exceptions to this rule are Yamamoto's 1st Bombardment Unit (Yamato, Fuso, Yamashiro), which will fire a far larger total of shells, as well as Nagato and Mutsu, which will fire some of their AP at trapped battleships in port.

Shell allocations on various targets

Ship...........Group....Target..............Main Bat...Secondary
Yamato..........1.......Navy Base.........720...............0
Yamato..........1.......Ewa....................0.............1,530 (6.1")
Nagato...........1.......Pennsylvania......150..............0
Nagato...........1.......Counterbat..........80...............0
Nagato...........1.......Navy Base..........50...............0
Mutsu............1.......BB Row..............200.............0
Mutsu............1.......Counterbat...........80..............0
Yamashiro......1.......Hickam AFB.......864.............0
Fuso..............2.......Wheeler..............864.............0
Myoko...........2.......Shofield..............300..............0
Myoko...........2.......Shofield..............300..............0
Hiei...............3.......Ford (N)..............180..............0
Kirishima.......3.......Ford (S)..............180..............0
Kongo...........3.......Cinpac/Sub.........180..............0
Hiei Class(4)..3.......Ewa.....................0..............2,400 (6")
Haruna..........3.......Cinpac/Sub.........180..............0
Mogami x 3....3......Oil Tanks............900..............0
Myoko x 3......4......Navy Base..........900..............0
CL - Counterbattery
DD - Counterbattery

Firepower summary (not including AP or anti-oilfield attack)

Type.....25 lbr eq......HE expended.............Total 25lbr effect
14"...........7.31.................2,448.......................17,895
16"...........9.34...................210........................1,961
18.1".......11.41..................720.........................8,215
8".............3.36.................2,400.......................8,064
6.1"..........1.87.................1,530.......................2,861
6".............1.8...................2,400......................4,320

Total - 43,316 25lbr shell equivalents (equal to 2,566 x 250kg bombs, or 855 Betty bomber attacks)

Base Effect Summary

Base.............Area*......25lbs**....AOA***.......Building****...Cas*****
Hickam...........73..........87...........48%...........80,041..............39
Wheeler..........60.........105..........58%...........80,041..............44
Ewa................39.........184.........102%..........36,674..............64
Ford (South)....33..........40...........22%...........16,675..............20
Ford (North).....24..........55...........30%...........16,675..............26
Cinpac/Sub.....25..........105..........58%...........33,350..............44
Schofield.........49...........41..........23%...........15,372...............21
Navy Base.......82.........143..........79%..........169,688..............55

* - Number of 100 x 100 yard target boxes.
** - # of 25lbr shell equivalents per 100 x 100 yard target box in base area.
*** - Total max. Area of effect of shells as a ratio of base area
**** - Total max. potential building damage area of shells
***** - Number of casualties expected per 1000 men in target area.

Vs. Penn - about 15 expected hits (16")
Vs. Drydock - about 61 hits
Vs. Cassin/Downes - 5hits
Vs Oil tanks - over 90% hit.
Vs. BB Row - about 12-14 hits per ship.

Effects of bombardment against oil tanks.

As previously noted, the berm system at Pearl Harbor was not capable of containing major spills caused by the intensive bombardment of the oil tank system. Aside from forcing the USN to evacuate Hawaii or face fuel starvation, a significant secondary effect of destroying the fields would be the potential to inundate the naval base with burning oil, perhaps destroying it.



F....Tanks......Rad/Rad...Area..........Field
1.......8............30/50.......7854
2......17..........132/152...72,581......2,052,750
3.......9............72/92.....26,590
4......27...........60/80.....20,105.......1,616,900

Tanks - number of tanks in field
Rad/Rad - radius of tank / radius of tank vs. near miss kill. (square feet)
Area - Area of tank (square feet)
Field - Field size, plus 15%.

Bombs required for specified effect in two tank fields:

Field.....................Tanks.............90% hit rate
East of Cinpac........17..................About 65
West of Cinpac.......27..................About 185


Bombs:

About 65 bombs are required to ensure that 90% of the tanks in the field east of Cinpac HQ (2,052,750 square feet) are either hit directly, or near missed within 20 feet. About 185 bombs are needed for the same effect in the field West of Cinpac. Once this level of destruction is achieved, presumably surviving tanks would be targeted individually when identified.

Shells:

Fewer shells will be required to ensure direct hits on tanks because a shell will at the targeted tank farm with a shallower striking angle than a bomb. This increases the target area/field area ratio.


Bombardment of airfields.

Hickam and Wheeler functioned as both as the most important fighter and bomber fields, but as the primary administrative depos for the Hawaiian air command. This is why these are earmarked for very heavy bombardment. Otherwise a primary motive for airfield bombardment is to try to destroy aircraft on the ground. Assuming good visibility, the effectiveness of shellfire against aircraft parked on airfields depends on the density of aircraft on the field, the area over which they are dispersed, and whether or not they are revetted or otherwise fortified from attack, and the type, power, and quantity of shells fired. Airburst A.A. shells and Type III incendiaries vs. aircraft were the most effective against parked in the open. The IJN later employed this technique during the Guadalcanal campaign,

"...They would deluge Henderson Field with 8-inch shells fitted with anti-aircraft time fuses that would burst the projectiles above ground and thus assure a wider scattering of fragments. The Combined Fleet fondly hoped this technique would devastate the Cactus Air Force."
Frank, Guadalcanal, 295


Only one time this method was employed by IJN battleships against an American airfield - the effects achieved were so severe that never again did the USN permit IJN battleships to approach Henderson Field uncontested. Only 104 Type III and 189 HE shells were employed. The apparent reason that the bombardment was so telling was because with AA and incendiary against brittle aircraft, the radius of effect of each shell expanded to it's full A.A. burst zone and/or submunition pattern.

Aircraft Area

The larger the aircraft, the more likely that it would be damaged by a single shell (more plane for the splinters to love). Area is taken as (Length+Span /4)^2 *3.1415

P40 - 107 square yards
SBD - 119 square yards
B-18 - 465 square yards
B-17 - 691 square yards

Lethal shell Area vs. Aircraft.

Type...........Square Yards vs. Aircraft
8".........................234
14".......................697
16".......................924
18"......................1183

Shell effect is measure in units of salvo boxes - the inherent pattern of fall of a salvo. Precisely how big this box should be is a matter of speculation,

http://ibiblio.org/hyperwar/USN/rep/Ley ... -78.3.html

From the performance off SAMAR, it can be concluded that the Japanese have failed to learn one of the axioms of fire control -- that in salvo fire the pattern must be large enough to allow for control error and insure hits once the mean range is established. Their pattern sizes were extremely small. Competent observers have stated and photographic evidence appears to verify the fact that the pattern size was in the neighborhood of 200 to 300 yards. This pattern size proved, after a trial of two and one-half hours, to be entirely too small to insure hits.

78-97

The enemy surface fire seemed to be much inferior to the standard of our navy. This may be due in part to the very small range patterns that the Japanese seem to use. The enemy range pattern, from all types of guns, seldom exceeded 50 yards with ranges up to 9000 yards. In agreement with this supposition is the fact that the number of near misses which did no damage to the ship was unusually high.


Tight patterns at sea were bad because ships could salvo chase, and so greatly reduce the PK of a densely packed group of shells. But vs. land targets, tight patterns were much more dangerous than wider ones because the objects of attention were stationary; their inability to dodge allowing the a smaller and tighter salvos to place a shell directly on the target more quickly, given average luck.

The first chart assumes the salvo pattern to be 40,000 square yards. PK of a miss against an aircraft within 40,000 square yard salvo box is:

((40000 - (Area of Aircraft)/ 40000)^shells fired * ((40000 - (Area of Shell Effect)/40000)^Shells fired

This chart shows the shells expended vs. aircraft type for 25/50/75% probability of kill. The percentage figures tell how many shells must be fired into a 40,000 square yard zone to achieve a 25/50/75% kill rate against the specified aircraft type.

Gun.....Aircraft........25%........50%........75%
8"..........P-40..........34...........82............163
8"..........SBD..........33...........79............157
8"..........B-18..........17...........40............79
8"..........B-17..........13...........30............60
14"........P-40..........14...........35............69
14"........SBD..........14...........34............68
14"........B-18..........10...........24............48
14"........B-17...........9............20............40
16"........P-40..........12...........27............54
16"........SBD..........11...........27............53
16"........B-18...........9............20............40
16"........B-17...........8............17............34
18"........P-40...........9............22............43
18"........SBD...........9............22............43
18"........B-18...........7............17............34
18"........B-17...........7............15............30

Smaller salvo patterns.

The IJN worked very hard to achieve the tightest salvo patterns in the world (200-300 yards off Samar at long range). Assuming that this translated into a box 275 yards long and 75 yards wide (20,625 yards), then

Number of shells required for a 14" AA shell scoring a 75% chance of damaging/destroying an aircraft with 40,000 square yard and 20,625 square yard salvo box:

Type.......40,000..............20,625
P40.............69.....................36
SBD............68.....................35
B-17............40.....................21

The tighter the salvo pattern, the more brutal the effect. For example, a bombardment of 100 x 14" AA shells vs. 18 x B-17 dispersed in a 60,000 square yard area should see around 16 of 18 aircraft destroyed or heavily damaged. Assuming that 24 SBD's were also in the target park with the B-17's, then about 18 of them would also be hit.

Type III Shells.

Gun.......Incendiary submunitions...........Area of scatter pattern.
18.1"...................996........................................50,595
16"......................735........................................39,195
14"......................480........................................19,960
8"........................198..........................................8,639
In the case of the Type III incendiaries, the device pretty much had to land on the aircraft to achieve a kill. For this reason, I'll assume the submunitions as having no lethal radius of destruction, and the aircraft radius at 1/2 it's area for HE effect


PK vs. aircraft for Type III incendiaries is nothing short of brutal.

Shell......Aircraft........Area of Effect..............75% coverage.........Pr. Hit
8".............P-40..............8,639................................6.................73%
8".............B-17..............8,639................................6................100%*
14"...........P-40.............19,960...............................2.................73%
16"...........P-40.............39,195...............................1.................64%
18"...........P-40.............50,595...............................1.................65%

(Vs. B-18, B-17, PBY types, certainty of a hit is about 100% for all shells).

In general, the larger the aircraft the less viable their deployment on Oahu in the face of naval bombardment. Small fighters and single engine bombers, especially near Wheeler, could have been dispersed and fortified against HE attack. (For example, if assuming a 40,000 square yard salvo box it would take 729 x 16" AA shells to destroy 50% of P-40's in an area 1/3 of a square mile when only 459 would be needed if targeting B-17's). Put another way, if Mutsu were hunting individual B-17's by indirect spotted fire, it might take around average of 17-20 big shells to hit each aircraft, assuming only one B-17 per 40,000 square yard salvo box. If Myoko were trying the same trick against a single P-40, it should take 82-100 (which is still a pretty good rate of return for an AA investment, all things considered). Shrinking the salvo box has the direct effect on the number of shells expended - half the box = half the shells for a hit.

With the Type III, the potential devastation is worsened by orders of magnitude. Where Mutsu needed 17+ shells to hit a B-17, now one single shell stands a reasonable chance of dropping a blowtorch right on the aircraft. The same 459 shells needed in the example above could, if Type III, cover almost 6 square miles of ground with a strong chance of a kill. For this reason, any IJN real-life Tinkerbell would have singled out this particular weapon for special production and deployment efforts.

glenn239
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(17) operational order - Day 1 only

Post by glenn239 » 17 May 2007 16:30

Flagship NAGATO HITOKAPPU-WAN
21 Nov. 41
YAMAMOTO, Isoroku
CinC Combined Fleet






Combined Fleet Order No. 1

A. The allocation of strength will be shown in the table below.

<See OOB post, Phase I and Phase II>


B. Movements of force.


1. General:

The Force will move out of HITOKAPPU-WAN on 26 November and proceed
without being detected, and taking every precaution to insure the secrecy of its movements, to the point (Lat 40° N, Long 170° W), set for 3 December. Refueling and supply will be carried at all available opportunities en route so that at 18:00 on X-1, the Force will be at the position 430NM, 347° from Point Z


(Point Z is Pearl Harbor, Oahu)

All ships carrying additional oil supplies will have exhausted their overloaded oil supplies by 06:00 on X Day. Overloaded oil will be consumed as late as possible in the voyage.

In the event that additional oiling is required, all Units of the Force will make provisions to use their heavy fleet units to refuel smaller vessels.

All commands will monitor their fuel expenditures. Annex A* denotes anticipated fuel usage. Without comprimising the basic mission objectives, commanders will take measures not to exceed these projections nor to burn fuel needlessly.
(* - not provided.)

Cancellation

Detection of the Task Force prior to X-Day:

If the task force is discovered by the enemy prior to X-Day, then it will
adapt the secondary attack mission. GHQ will confirm by prearranged
signal that the Force will implement Combined Fleet Order No.2*

(*- not provided. Fleet Order No.2 would specify the initial invasion of Midway using the Kauai Invasion Force with the Main Body and Strike Force seeking an opportunity for battle. Then the bulk of forces would return to the Marshall Islands to prepare for an attack on Samoa and Johnston using the elements of South Seas Force and 7th ID already at the Marshalls.)

Movement, Supply Unit:

At 18:00 on X-1 the SUPPLY UNIT will commence withdrawal from Point X at utmost speed (about 16-18kt) to the point Lat 40° N, Long 170° W, ensuring not to approach within 800NM of the MIDWAY ISLANDS. The SUPPLY UNIT will then return to YOKOHOMA at utmost speed, taking precaution to ensure the secrecy of its movements. It will replenish, and arrive at Kwajalein on or about X+15


Movement and attacks, Strike Force

General: Irrespective of any other consideration, the Strike Force shall consider as the highest priority the freedom and ability to conduct aerial operations.

At 6:00 on X-1, the Strike Force will proceed to arrive at the point from which the airplanes will be launched at 0600 hours on X-Day; 200 nautical miles north, bearing 350° from Point Z. Air attacks will be made against enemy carriers and important air bases at or near OAHU:

1) The First Attack Unit will concentrate on air bases and aircraft carriers.
2) If the first Attack Unit meets organized resistance, then the Second Attack
Unit will concentrate on enemy air bases or carriers.
3) If the First Attack Unit has established air superiority, then the Second Attack Unit will target SCHOFIELD BARRACKS and HICKAM FIELD.



The First Attack Unit will employ AIR ATTACK METHOD A*.
The Second Attack Unit will employ AIR ATTACK METHOD B*.

With the exception of the First Attack Unit, or by special order from CinC, no Attack Units shall employ METHOD A against any target within Anti-Aircraft range of enemy fleet units based in Pearl Harbor. If casualties are deemed heavy by STRIKE FORCE commander, then Attack Units may employ METHOD C* for targets within Anti-Aircraft range of enemy fleet units. This restriction applies so long as the majority of enemy fleet is within Pearl Harbor.

The preceding restriction does not apply with respect to the elimination of enemy airpower or aircraft carriers.

(* - Method A: Mixed attack groups with no altitude restrictions near the harbor.
Method B: Level bombing from 10,000 feet.
Method C: Level bombing from 20,000 feet.)


The STRIKE FORCE will ensure that the First and Second Attack Units are recovered and re-armed without delay. The target of the Third and Fourth Attack Units are at the discretion of the STRIKE FORCE commander according to the following priorities:

1) The destruction of operational enemy carriers.
2) Establishing air superiority over Oahu.
3) The destruction of other ships at sea.

Unless the preceding list of priorities dictate a contrary course of action, after launching attacks, the STRIKE FORCE will move to a point bearing approximately 318°, 178NM from Point Z for recovery. After recovery of the aircraft of the First and Second Attack Units, STRIKE FORCE will maintain the maximum separation from OAHU during rearming consistent with the intended position of the launch of the Third Attack Unit from 200NM, bearing 318° degrees from Point Z:.


After dusk, with the recovery of the Fourth Attack Unit, the STRIKE FORCE will establish night cruising order and retire to a holding position 295°, 255NM from Point Z, remaining there until approaching the launch position for X+1. STRIKE FORCE shall detach Abukuma, Minegumo and Asagumo from night cruising order for the purpose of advanced scouting to the X+1 launch position.

X-Day Reconnaissance: Except with respect to the targeting of the Attack Units, the STRIKE FORCE is not responsible for searches during X Day. If designated scouting units are unable to accomplish their search tasks, then STRIKE FORCE will make search missions in appropriate sectors, such that STRIKE FORCE maintains a 360° situational awareness.

Combat Air Patrol, X DAY: The STRIKE FORCE will provide assistance from air attack to the following friendly units: MAIN BODY, KAUAI INVASION UNIT, if these come under attack. Aside from generally maintaining a station that intersects the line between MAIN BODY, KAUAI INVASION UNIT, and Point Z, the STRIKE FORCE will not take any action, or maintain a standing patrol over any other friendly formations other than the STRIKE FORCE.

Movement and attacks, Strike Force, X+1:

The STRIKE FORCE will be in a position approximately 289°, 188NM from OAHU at 0600 X+1. The STRIKE FORCE will make attacks in conformity to the instructions of the MAIN BODY. The MAIN BODY will order TYPE, METHOD, and LOCATION of attacks required:

Type A: Attacks against enemy ships.
Type B: Attacks against enemy air bases and/or carriers.
Type C: Attacks against enemy coastal defenses.
Type D: Attacks against enemy naval base.

If MAIN BODY does not communicate in time to meet the launch deadline, then STRIKE FORCE will adapt target TYPE B for Attack Unit 1 and TYPE A for Attack Unit 2, with subsequent Attack Units operating at the discretion of the STRIKE FORCE commander.

Regardless of any other consideration, STRIKE FORCE will attack as the highest priority any enemy force that poses a threat to the STRIKE FORCE.

Reconnaissance, X+1 (Omitted.)

Combat Air Patrol: Aside from self-protection, STRIKE FORCE will maintain standing air patrols over KAUAI INVASION FORCE from 0600. Embarked elements of 24th AIR FLOTILLA shall be readied for action by 0400 X+1, and shall be considered adequate for this task.

Upon receipt of the appropriate signal from the KAUAI INVASION FORCE, STRIKE FORCE will transfer to Kauai Tier 1 reinforcement aircraft.

After dusk, with the recovery of the Fourth Attack Unit, the STRIKE FORCE will establish night cruising order and retire to a holding position 282°, 263 NM from Point Z, remaining there until approaching the launch position for X+2. STRIKE FORCE shall detach Abukuma, Minegumo and Asagumo from night cruising order for the purpose of advanced scouting to the X+2 launch position.

X+2 movements and strikes.

STRIKE FORCE will be in a position approximately 273°, 200NM from OAHU at 0600. STRIKE FORCE will launch Attack Units 1 and 2:

Attack Unit 1 shall strike enemy air bases and/or carriers.
Attack Unit 2 shall strike enemy naval base.

Upon recovery of attack units, STRIKE FORCE will retire towards POINT W* at utmost speed (approximately 24kt) until 6pm, and then retire at 16kt-18kt.

* - Point W is refueling rendezvous bearing 173 degrees, 100NM from Johnston Atoll.

Reconnaissance: (Omitted)

Combat Air Patrol: STRIKE force will provide air escort as the Force withdraws.

Movement of the MAIN BODY

After final refueling at Point X, the MAIN BODY will proceed at moderate speed (approximately 16 knots) in accompaniment with the KAUAI INVASION UNIT to a position 345°, 240NM from Point Z. From 0600, the MAIN BODY will accompany the KAUAI INVASION UNIT, such that by 12:00 on X-Day it is 320°, 250NM from Point Z and at 18:00 it is 305°, 195NM from Point Z. The MAIN BODY will not enter within a 200NM radius of enemy anchorage at Point Z until about 18:00.

From 18:00, the MAIN BODY shall escort the KAUAI INVASION UNIT to a position bearing 287°, 114NM from Point Z by 24:00. After establishing the safety of the KAUAI INVASION UNIT, the MAIN BODY shall attack the enemy at PEARL HARBOR.

Reconnaissance:

Morning: From the position at 0600 on X-Day, the MAIN BODY is responsible for scouting to the north from 270° to 90° inclusive to a distance of 150NM. Air searches shall commence at 0800.320°

Afternoon: From the position 250NM, 320° from Point Z, the MAIN BODY shall conduct searches from bearings 248° to 338 °, and from 60° to 154°, to a distance of 160 or 250NM

MAIN BODY movements, X+1.

After securing the environs near the KAUAI INVASION UNIT by 24:00 on X Day, the MAIN BODY shall close upon and annihilate the enemy MAIN BODY and the enemy FLEET TRAIN. To the extent possible, the MAIN BODY will concentrate its efforts on the destruction of the following types of ships:

1) Enemy capital vessels (aircraft carriers, battleships).
2) Enemy heavy cruisers.
3) Enemy fleet auxiliaries.

The MAIN BODY shall communicate to the STRIKE FORCE, specifying in a timely fashion the TYPE, METHOD and LOCATION of supporting air attacks.

Upon completion of the DECISIVE BATTLE, or if the enemy eludes a DECISIVE BATTLE, the MAIN BODY shall attack OAHU. If enemy fleet is in PEARL HARBOR, then MAIN BODY will assume SPECIAL BOMBARDMENT FORMATION NO.1. If the enemy fleet has fled the harbor, then the MAIN BODY will assume SPECIAL BOMBARDMENT FORMATION NO.2. Upon the completion of
TYPE C preparations by STRIKE FORCE against enemy batteries at HATCH, WILLISTON, RANDOLPH and CLOSSON, MAIN BODY shall bombardment OAHU as per the attached schedule*. Destroyers will enact enaku choka shageki tactics.



* - see "Bombardment" post.

<Bombardment details in the event of an attack on the Pacific Fleet in Pearl Harbor are omitted - this would not have occurred>)


All units will take care not to expend without cause the ammunition reserved for the bombardment of OAHU.

Reconnaissance, X+1: (Omitted)

Main Body, X+2


Upon completion of the battle of Oahu, the MAIN BODY shall withdraw to the rendezvous point with the STRIKE FORCE: 0600 hrs, 273° 200NM from Point Z. From this position the MAIN BODY shall, during its withdrawal to POINT W, support the operations of the STRIKE FORCE and KAUAI INVASION UNIT.

KAUAI INVASION UNIT.

From 18:00 X-1, the KAUAI INVASION UNIT will proceed at utmost speed
(approximately 16 knots) south in accompaniment with the MAIN BODY. It will divert westwards to maintain a 200nm separation from OAHU, and reach a position bearing 305°, 195NM from POINT Z at 18:00, X Day.. KAUAI INVASION UNIT will then proceed to KAUAI at utmost speed and debark with utmost speed the Army units ordered to seize enemy airbases at Barking Sands, Burns Field, and Mana at 12:00 on X+1.

Reconnaissance, Morning: From the position at 0600 on X Day of 345°, 240NM from Point Z, the attached seaplane tender of KAUAI INVASION UNIT is responsible for air searchers from bearings 180° to 270° to a distance of 300NM. Air searches will commence at 0800.

Reconnaissance, Afternoon: From the position 211NM, 307° from Point Z, the attached seaplane tender shall scout bearings 133° to 272° to a distance of 250NM.

Movements, X+1.

Upon completion of debarkation, the transport elements of the KAUAI INVASION UNIT, less Chiyoda and Asagiri, will proceed at utmost speed, approximately 16kt, towards POINT W until 400NM from OAHU. It will then continue to withdraw to POINT W.

Reconnaissance: (Omitted)

Movements, X+2.


Upon launch of morning searches, the KAUAI INVASION UNIT may proceed westwards to a recovery position. Once aircraft are recovered, the Unit will withdraw towards POINT W at high speed (approximately 24kt) until 18:00, at which time the Unit will continue to withdraw at moderate speed.

Reconnaissance: (Omitted).

Scouting Unit

FRENCH FRIGATE SHOALS FORCE:

At 18:00 on X-1, the FRENCH FRIGATE SHOALS FORCE will separate from the MAIN BODY and proceed directly to the FRENCH FRIGATE SHOALS at 24kt.

AT 0800 on X Day, FFS FORCE will commence air search activities. FFS FORCE is responsible for a search sector bearing 190° to 280° from it's position at 0600, to a distance of 300NM. In addition, the FFS FORCE will cover a sector from 20° to 110° to a distance of 100NM from its position at 0600.

Afternoon: From a position 60NM, 59° from FRENCH FRIGATE SHOALS, the FFS FORCE shall conduct searches from bearing 160° to 286°, to a distance of 250NM.

FFS - Day X+1

(Omitted)

Day X +2, and withdrawal.

(Omitted)

HAWAII SCOUTING UNIT.

The HAWAII SCOUTING UNIT shall detach from the MAIN BODY at 0600 on X Day from a position bearing 345° and 240NM from Point Z. From there it will move at high speed (approximately 24kt), such that it is in a position from Point Z 20°, 190NM at 12:00 and 42°, 197NM at 18:00.


From this point, the HAWAII SCOUTING UNIT shall make a high speed dash (approximately 24kt) to the 0600, X+1 scouting zone bearing 140°, 165NM from Point Z.

X-Day Scouting

Morning. HAWAII SCOUTING UNIT is responsible for a sector bearing 180 to 90 degrees from its position at 0600 to a distance of 300NM. Scouting will commence at 0800.

Afternoon: From a position 200NM, bearing 20° from Point Z, the HAWAII SCOUTING UNIT shall search a sector to the south from 209° to 83°

X+1.

Reconnaissance: (Omitted)

Movement.

Upon recovery of scouting aircraft on the afternoon of X+1, the HAWAII SCOUTING UNIT shall withdraw to POINT W at a speed of about 18kt, taking care to maintain a separation in excess of 200NM from POINT Z.

Johnston Island Force.

<omitted>

Actions of the 6TH FLEET

A submarine recon support force, taking care to conceal its position, will be positioned at the FRENCH FRIGATE SHOALS by 1300 on X-1, unless it is occupied by enemy forces. They will enter the atoll at 0600 of X day and support the reconnaissance forces of the 24th AIR FLOTILLA with supply and, after 0800, navigational assistance, where necessary.

<Remaining orders for 6th Fleet submarines omitted>

24TH AIR FLOTILLA.

3 H6K reconaisance aircraft will fly to the FRENCH FRIGATE SHOALS by 0600 on X-Day. If unoccupied by the enemy, they will refuel and commence an air search at 0900 hours on X day and return to the FRENCH FRIGATE SHOALS.

3 H6K reconaisance aircraft will commence air searches from the Island of Hawaii to the northwest at 0830 hours on X Day. These aircraft will return to FRENCH FRIGATE SHOALS.

Upon the reciept of the appropriate signal, 6 H6K reconaisance aircraft will proceed to the Kauai anchorage, to be available for searches as of 0600 X+1. Additional forces will stand by in the Marshall Islands to support these reconaisance efforts as circumstances
dictate.

<search area responsibilities for 24th A.F. omitted - see recon post>


xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx



Ultrasecret Operation Order 1 (essentials).


Flagship HIRYU, HITOKAPPU-WAN
25 Nov 41
Yamaguchi, Tamon
Task Force Commander




Task Force Order



A. The plan for the air attack against HAWAII is as follows:

At 0600 hours on X-Day the First Attack will take off from a point 200
nautical miles bearing 350° from Point Z. At 0645 hours the Second Attack Unit
will take off from a point 190 nautical miles bearing 350° from Point Z.

When all the airplanes of the Second Attack Unit have taken off, the force
will move to a supporting position of approximately 318°, 178NM from Point Z.


It is estimated that the airplanes of the First Attack Unit will return
between 0930 hours and 1000 hours and the airplanes of the Second Attack
Unit between 1015 hours and 1030 hours.

When the units return preparations will be made immediately for the next
attack. The third wave will be launched at 1245 hours. The fourth wave will be
launched at 1330 hours. Upon launch of the Fourth Wave, the STRIKE FORCE will proceed to a support position approximately 295°, 175NM from Point Z. Upon recovery of the third and fourth attack units, the STRIKE FORCE will retire towards the nighttime holding area.


B. In the event that the enemy has maintained strict lookouts and opposition
is strong, the units will attack in the following order, with only a slight time interval between attacks.


(1) Fighter Unit
(2) Airfield attack Unit

In the event of alerted opposition, the Torpedo Bombing Unit will not attack inside the harbor, but will rather attack ships outside of Pearl Harbor or, failing this, immediately return to the STRIKE FORCE.

2. Second Attack Unit.

The entire unit will attack at about the same time.

All forces will employ attack Method B, from an altitude of about least 9,000 feet.

The fighter unit will provide close escort. It will not conduct low-level attacks.


If First Attack Unit has signaled success, then Second Attack Unit will target:

Zuikaku Group: Hickam Field
Shokaku Group: Hickam Field

Kaga Group: Schofield Barracks
Hiryu Group: Schofield Barracks
Soryu Group: Schofield Barracks

If the First Attack Unit does not signal success, then the Second Attack Unit shall target:

Kaga Group: Wheeler Field.
Shokaku Group: Ford Island
Zuikaku Group: Hickam Field
Hiryu Group: Kanoehe Naval Air Station
Soryu Group: Barber's Point Air Station.

C. Regrouping and returning:

a. The regrouping point following the attack will be 20 nautical miles
bearing 340° from the western tip (KAENA POINT) of OAHU.

The airplanes of the FIRST ATTACK UNIT will rendezvous at an altitude of
1,000 m (if clouds are present at about that altitude the rendezvous will be
made below them).

The aircraft of the SECOND ATTACK UNIT will rendezvous at an altitude of
3,000 m.

b. The attack units of the FIRST ATTACK UNIT will wait at the regrouping
points for about 30 minutes. After making the rendezvous with the fighter
striking units they will return to their ships.

The attack units of the SECOND ATTACK UNIT will wait at the regrouping
points for about 15 minutes. If the rendezvous has not been effected within that time, the SECOND ATTACK UNIT will return to their ships. Designated pathfinder aircraft will remain at the rendezvous point for an additional half an hour.

The fighter striking units will cover the return of the main attack units
and intercept any enemy pursuit planes.


Reserve Attack Unit.

The reserve attack unit will stand in readyness for immediate operations against targets on land or at sea. It is not to be committed to action except by direct order from the flagship.

D. Organization and targets of Air Attack Units


First Attack Unit.

Observation and Command

Comdr. FUCHIDA
1 Aircraft
Two No. 25, Land Bombs (250 kg.)
Target: Cinpac HQ.

Group 1

Lt. Comdr. MURATA
26 Aircraft
Torpedo bombing attack
One Type-91 Aerial Torpedo.
Target: battleships, aircraft carriers


2 Group

Lt. Comdr. EGUSA
Type 99 Carrier Bombers (117 total)
Dive bombing attack
One No. 25 Land Bomb (250 kg.)
Target: Air bases


12 Special Attack Unit
Lt. Makino
27 Aircraft
Target: Wheeler Field

13 Special Attack Unit
Lt. Comdr. Egusa
18 Aircraft
Target: Barber's Point NAS

14 Special Attack Unit
Lt. Kobayashi
18 Aircraft
Target: Kanoehe Bay Naval Air Station.

15 Special Attack Unit
Lt. Comdr. Takahashi
27 Aircraft
Target: Hickam Field

16 Special Attack Unit
Lt. Sakamoto
18 Aircraft.
Target: Ford Island Naval Air Station

16 Special Attack Unit
Lt. Sakamoto
9 Aircraft.
Target: Wheeler Field


3 Group
Lt. Comdr. ITAYA
Type ZERO Carrier Fighters (54 total)
Air Control and Strafing Attack
Two 20-mm. Mgs.
Two 7.7-mm. Mgs.
Target: 1. Airborne aircraft.

Target: 2. Airbases.

1 Fighter Striking Unit
Lt. Comdr. Itaya
9 Aircraft
Target: Wheeler Field

2 Fighter Striking Unit
Lt. Shiga
9 Aircraft
Target: Wheeler Field

3 Fighter Striking Unit
Lt. Suganami
9 Aircraft
Target: Ford Island

4 Fighter Striking Unit
Lt. Okajima
9 Aircraft
Target: Hickam Field

5 Fighter Striking Unit.
Lt. Sato
9 Aircraft
Target: Barber's Point Airfield

6 Fighter Striking Unit
Kt. Kaneko
9 Aircraft
Target: Kanoehe Bay Naval Air Station.


SECOND ATTACK UNIT


Type 97 Carrier Bombers (105 total)
Horizontal bombing attack
One No. 25, Land Bomb (250 kg.)
Six No. 6, Ordinary Bombs (60 kg.)

Target: Schofield Barracks, Hickam Field


3 Group
Lt. SHINDO
Type ZERO Carrier Fighters (36 total)
Close Escort
Two 20-mm. Mgs.
Two 7.7-mm. Mgs.
Target: Airborne airplanes


Reserve Attack Unit.

11 Special Attack Unit.
Lt. Comdr. Chihaya
One No. 25 Land Bomb (250 kg.)
18 aircraft
Target: None. In reserve, aboard Akagi.

E. Preparations for the next attacks.

The Third Attack Unit shall be readied for launch by 12:45

The Fourth Attack Unit shall be readied for launch by 13:30

Launch times will not be delayed to accommodate stragglers.

Third Attack Unit.

Third Attack Unit shall be prepared for naval combat.

<Rest of Third Attack Unit order ommitted>

Fourth Attack Unit.

Fourth Attack Unit shall be prepared for land attack, attack Method B.

The targets of the Fourth Attack Unit shall be:

Zuikaku Group: Cinpac HQ and Submarine Base.
Shokaku Group: Ford Island Naval Air Station
Akagi Group: Naval Base.
Kaga Group: Hickam Field
Hiryu Group: Wheeler Field
Soryu Group: Schofield Barracks

<remainder of order ommitted>

E. Reconnaissance:

1. The reconnaissance seaplanes of Cru Div 8 (DAIHACHI SENTAI) will be launched about 0730. They will search over as wide an area as possible between the Task Force and the enemy and along the channels on the east and west sides
of OAHU. They will report the presence of enemy surface force moving out to
attack and its movements, the presence of counter-attacking enemy airplanes
and their movements, etc.

2. Reconnaissance just before the attack.

One reconnaissance seaplane of Cru Div 8 (DAIHACHI SENTAI) will be
launched at 0730 hours on X-day. It will reconnoiter the LAHAINA anchorage, and report whether or not the enemy fleet units (particularly carriers and battleships) are at this anchorage.

F. Air Patrol:

From 1 hour before sunrise until 45 minutes after sunset on the day of
attack, Air Patrol Readiness Disposition 1, Plan B will be used for STRIKE
FORCE.

glenn239
Member
Posts: 5590
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

(18) Conclusion

Post by glenn239 » 17 May 2007 16:31

Tinkerbell anticipates a Guadalcanal-style campaign in Hawaiian waters during the period December/January, culminating in the assault on the island fortress via the Kaneohe Bay region. A successful end-game position for the attackers would see, after the consumption in excess of 500,000 tons of oil from the strategic reserve, the occupation of Honolulu and the cessation of major supplies reaching the garrison from the West Coast through the direct interdiction of all three deepwater ports on the island.

The choice of landing on the east coast allows the attackers to avoid (at least temporarily) the main concentrations of defensive power massed on the central plain of the island. As to the question of a landing, much would depend on American dispositions made after the 7th, the deceptive measures undertaken by the Japanese designed to divert the main strength away from the real danger from the east, and in the quality of the prepatory bombardments made against coastal defenses, reserves and communications.

From Waimanalo and Kailua it is about 6 miles to the passes overlooking Honolulu (now Wilson Tunnel and Nuuanu Pali Tunnel on Hwy 61/63). If the Japanese could seize these positions and push beyond them towards Fort Shafter and Aliamanu Crater before the defenders could react in strength, then the IJA would have established the basis by which the 1st Artillery Regiment could dominate Pearl Harbor, Aliamanu, Honolulu and Hickam Field. Conversely, if the assault failed to take the high ground overlooking Honolulu, this might result in the east coast landings being contained; a landing on the west coast by 2nd I.D. might prove necessary as the next step.

Given the difficulties a defender would have in moving about the island in the face of hostile air and naval power, the US Army plan for protecting Oahu relied to a dangerous degree upon the ability of the central reserve forces to access by road the threatened location and conduct a counterattack. While it is true that it would be difficult to cross the mountains, the Japanese did not need to do that in order to use heavy artillery to hit the bases on the other side. Certainly the US Army required a presence on Hwy 63 in the Kaneohe area in regimental strength - the IJN/IJA gunfire tactics on display at Amoy years prior to the war emphasized the destruction of key bridges and deep attacks on reserves, which could have prevented the timely arrival of reinforcements at Honolulu and Kaneohe.

Regardless of any other consideration, a protracted land battle on Oahu would have been a brutal artillery slugfest, with the scale of firepower employed by both sides making it the equivalent to a 1941 Okinawa. The battle would devastate the island:

Oahu garrison firepower guesstimate by shell type
(HE types only)

Type...........Qty..........25lbr..........Total
240mm......3,000.........6.75.........20,250
8"..............3,600.........3.08.........11,088
155mm.....139,355.......2.9.........404,129
75mm.......415,318.......0.5.........207,659
81mm........15,395........0.5...........7,698
Total.........................................650,824 25lbr equivalents

Against this ante, neither the Japanese carriers nor the Japanese fleet could reply with their full potential against the island. A rough guess might see an average of about 30% of the fleet's total carried shells per sortie and 35% of the carrier's firepower per sortie used against Oahu. With 3 total sorties to Hawaii by the IJN, this might be:

Japanese Oahu firepower summary
(25lbr equivalents).

IJN surface units: 290,250*
Carriers (excluding CVL): 71,300
Artillery Brigade: 567,400
IJA divisions: 114,000
Land Based Airpower: 319,391

* - IJN contribution may be lower due to limited stocks of shells onhand. IJN shell inventories in Dec 1941 unknown.

Total: 1,362,341 25lbr equivalents.

As a comparison:

Okinawa naval firepower summary , USN, 1945

Type Rounds Fired

Star illumination, 5-inch 66,653
High-capacity fragmentation, 5-inch 432,008
High-capacity fragmentation, 6-inch 46,020
High-capacity fragmentation, 8-inch 32,180
High-capacity fragmentation, 12-inch 2,700
High-capacity fragmentation, 14-inch 16,046
High-capacity fragmentation, 16-inch 4,411

Total 600,018

Source: Appleman et al., Okinawa, 500.

= about 1,100,000 25 lbr equivalents

http://www-cgsc.army.mil/carl/resources ... _13.asp#93


If this scale of firepower (particularly that of the 1st Artillery Regiment) could be deployed against Oahu and kept in supply, then the Japanese should win the battle. The side which lost would be the side that could not deliver the material and reinforcements necessary to continue the fighting (both sides would need hundreds of tons of supplies per day). Control of the sea would be therefore be paramount in determining ultimate victory.

Naval Battle.

Should the movement of heavy forces towards Oahu have been detected prior to the war it would have prevented any chance of conquering the island. A larger fleet attacking Oahu on the 7th obviously stood a higher chance of being detected prematurely because it would contain most of the major combat elements of the Japanese fleet. USN records give an idea of the ability of the Pacific Fleet to track IJN units in the 6 months leading up to the war,

2. Changes of call signs, addresses, use of alternate, secret, tactical, and special calls, greatly complicates the identification of units and the
reconstruction of the naval organization afloat and ashore. The Japanese Navy shifted its call signs on 1 May, 1 November and 1 December 1941.
Shortly after the 1 November change, the Japanese began using a "blanket broadcast" system in which no originator or addressee appeared, these being
presumably buried in the cipher text.
3. It has been a general rule that when a unit was not heard originatingtraffic or using tactical circuits it was presumed to be in port or in a navy yard in a relatively inactive status.
4. It is to be noted that for the above reasons the simultaneous location of each Division of Battleships, cruisers, destroyers, carriers, or submarines is not possible. Therefore, the location of Fleet Flagships and some subordinate units of the above types must be relied upon to establish the presumed locations or activity of the remainder of the related lower echelons.

5. During the past six months, fleet intelligence records show that the occasions when uncertainly existed as to the exact location of certain types


Type.....................D/U......N/P.........R/P
BB.........................70.......7..........8-14 days
CA(1st Fleet).."Almost continuous absence of positive indications"
CA(2nd Fleet*).......113.......8.........10-20 days
Cru Div 7**..............63.......6..........8-16 days
Destroyers........Indefinite...7..........9-33 days
Carriers***.............134.....12.........9-22 days
CV Div 2................84.......8..........8-22 days
PHA, Vol 23 no 1386


D/U = Number of days of uncertain location (out of 180 days)
N/P = Number of periods of uncertainty.
R/P = Range in days of period of uncertainty.

* - CA, 2nd Fleet less CA division 7
** - very active during period.
*** - less carrier Division 2.

A lack of information on the whereabouts of IJN units was the norm, not the exception. And when ships were silent (as they would be in this scenario), they were assumed to be in port and inactive, not sneaking up on Oahu. On top of this, the considerable efforts on the part of the Japanese at signal deception and emission control makes it seem probable that the additional strength committed to Tinkerbell would not result in detection prior to the attack on the 7th of December.

Initial phase - Dec 7th - 10th

The employment of the IJN battleline off Oahu shifts the onus for the destruction of the American fleet from Yamaguchi to Yamamoto, thereby allowing Kido Butai the freedom to concentrate more of the initial raids' destructive potential upon the air bases on Oahu. And as devastating as the historic raid was to the USAAF, it does not compare to this one, which is about 40% stronger due to the most effective platforms (Val dive bombers) being concentrated exclusively upon airfield work. When the third and fourth raids arrive on the afternoon of the 7th, Oahu will still be 'down' hard - coordinated aerial resistance will be trivial. (The anticipated results being sufficient to allow the diversion of resources necessary for a major attack on Schofield during its period of maximum vulnerability).

Aircraft status, Wheeler Field, 9 December

Type......On 7th........Op...RL....LTR......Fire.....Oth
P-40B......88............25....9........5.........36.......13
P-40C......13.............2.....4........0..........4.........3
P-36A......39............24....2........2..........5.........6
P-26A.......8..............2.....0........0..........4.........2
O-47B......1...............1
A-12A.......4..............1.....0........0..........0.........3
B-12A.......3..............2.....1
B-18.........1..............1
Light.........8..............1.....2........0..........3.........2
vol 19 , pg3640

RL = Repairable locally
LTR = Required reciept of major components from mainland
Fire = Destroyed by fire
Other = Destroyed by other cause

The reduction of the torpedo bombing element to 26 aircraft and the elimination of the level bombers from Battleship Row altogether would allow a greater potential for element of the USN battleline to "escape" to sea - perhaps as many as 4 of Kimmel's heavyweights will assemble south of the harbor entrance during the morning of the 7th. Yamaguchi therefore will have two targets for his two afternoon strikes - the Enterprise carrier group west of Oahu and battleship group south of Oahu (and any ships sunk now won't be repaired and refloated). In all probability, he will split his third and fourth waves between them, destroying the carrier task force in one strike and crippling the battlewagons.

The position of the USN carriers would be fairly desperate from the start. With the anticipated scale of coverage by IJN reconnaissance assets and the elimination of Oahu as a factor, the situation would see both USN flat tops groping for the information needed to counter the powerful blows Yamaguchi could muster against them. With so few fighters on either US carrier, and as many as half the dive bombers or more committed to searching, Kido Butai stands a good chance of sinking both US carriers with little damage in return.

The movement of the Main Body towards Oahu on the evening of the 7th anticipates a big naval battle commencing December 8th while Oahu's air bases would still be reeling. The main aerial contribution on the American side, save for Enterprise survivors would come from the Lexington group. Whatever airpower Oahu could muster (including Enterprise's) would probably be thrown onto the scales against Yamamoto. Lexington, lurking to the northwest, may also be compelled to offer support against Yamamoto's Main Body instead of the more dangerous activity of stalking Yamaguchi (in this respect, Yamamoto obsolescent tubs perform handsomely as a diversion and as a bomb magnet). The decision not to provide the Main Body with an air escort during the 8th might see some damage scored against the Main Body by these attacks. (It is judged that Yamaguchi's Zeros would do better service making powerful, concentrated attacks rather than guarding Yamamoto in penny-packets). In any case, Lexington's position, probably generally known from the afternoon of the 7th because of her proximity to the position at French Frigate Shoals, will be discovered by the wide-ranging IJN search on the 8th, and she and her escorting cruisers, without adequate defenses, will then be dispatched by Yamaguchi.

With both USN carriers sunk and the Pacific Fleet driven off, the Japanese would have been free to work over Oahu, concentrating on the oil storage system as well as continuing attacks upon the air base network. Once the oil facilities and reserves were destroyed, the USN Pacific Fleet would have no choice but to immediately withdraw to California.

It is possible that the rendezvous of the Main Body with the Strike Force called for on the 9th will not occur - the Main Body might require more time to mop up USN stragglers and bombard Oahu. If so, then the withdrawal towards Johnston on the morning of the 9th might be put off until dark.

Phase II - 14th to 16th.

By the 14th there would be as many as 8 IJN carriers and an airbase at Barking Sands, backed by a network of seaplane searchers casting for prey far to the east of Maui and the Big Island. It would be suicide for Saratoga to contest the 2nd Phase landings. Her best options would be to either to stand clear of the fighting entirely, or risk battle with the Bettys of Barking Sands so that she could deliver aircraft to Oahu. In any case, since Saratoga was incapable of supplying the numbers necessary to contest Yamaguchi's domination, and Hawaii was too far for single-engine aircraft to fly to directly, the USN would not have the resources necessary to contest the fall of Maui and Hawaii by the 16th, nor to shield Oahu.

During this phase Yamaguchi would be able to hit Oahu repeatedly while providing coverage for the invasion transports. (This ability to concentrate forces on one axis being the payoff for taking Kauai before Maui).

The bases captured on Kauai, Molokai, Maui and Hawaii between the 8th and the 16th give the Japanese the resources necessary to overpower Saratoga if she chooses to approach Hawaii while Yamaguchi replenishes in the Marshalls (the IJN carriers are absent from the 17th to the end of the month). With bases on 4 islands to hit and a carrier able to attack one island at a time, the USN Pacific Fleet would not have the ability to contest the air blockade at Oahu until the arrival of the Atlantic Fleet carriers at San Francisco by early January.

It can be assumed that Oahu, despite air attacks from the other islands, probably would experience a limited revival of airpower in the absence of Kido Butai. In particular it can be anticipated that Short's work at fortifying Wheeler would be redoubled. When the IJN returns at the end of the month, Oahu's air bases will again be the target of powerful blows.

Phase III.

The composition of the Japanese carrier strike force will be weaker in Phase III and IV due to increasing attrition.

Guesstimated combat aircraft losses, Kido Butai, Dec 7th-16th.

Target..............A.A.....CAP
Enterprise.........2...........5
Lexington..........2...........6
Fleet(at sea).....10..........0
Oahu......................64*
= 89 aircraft lost.

* - 4-5 aircraft lost per raid to AA fire, plus about 20 lost to the residual fighter defenses

Replacements available, Marshall Islands.

B5N1 (12) Tateyama Air Group
B5N2 (18) Ryujo Air Group
Zero - (7) 22nd Air Flotilla
Claude (16) Yokosuka Air Group
Claude (32) 24th Air Flotilla
Val - (12) Yokosuka Air Group
B4Y1 - (8) Hosho Air Group

Hypothetical Phase III Kido Butai air strength.

Carrier.......Zero......Claude.......Val.......B5N1......B5N2.....Total
Kaga...........26...........0............22..........6..............21........74
Akagi..........27...........0............15..........6..............21........67
Hiryu...........20...........4............17..........0..............18........59
Soryu..........22...........5............18..........0..............18........63
Zuikaku.......15...........4.............21.........0...............25.......64
Shokaku......15...........3.............21.........0..............26.......64
..................125.........16...........114.......12.............129.....396


Situation on Oahu

When the IJN retreats on the 16th, Oahu is blockaded by about 175 aircraft of all types based on the outlying islands - more than Saratoga can handle until reinforced (and dicey even then). In addition, IJN 6th Fleet submarines will have established an advanced base at Maui, and will use it in order to make patrols off the West Coast as well as locally. The greatest vulnerability of Oahu to these efforts would be food supply. But another concern for Short might be AA ammunition - Oahu's 109 x 3" AA guns had 150,000 rounds available - about 70 minutes of fire at a max rate of 20 RPM. It is possible that AA ammunition depletion might become a factor towards the end of December.

The necessity of delaying the main invasion for three weeks means that the defenders of Oahu would have had plenty of time to dig in. This might cause no end of grief for invading forces if the places chosen for such efforts were in the correct sectors (ie, the east and west coast instead of north and south). However, the delay also would allow the Japanese to conduct extensive air raids on Oahu's defenses, and to collect the intelligence on American troop concentrations necessary to moot these preparations.

US Options.

While it would have been bad strategy to do so, it is possible that an American knee-jerk response to the sudden siege of Hawaii would be to cast aside the bedrock of military policy - Rainbow Five's identification of Germany as the most dangerous foe - and instead have attempted a counter-blow to contest the pending fall of Hawaii. For Japan such a move would have been highly desirable. Not only would her most important ally Germany gain breathing room against western pressure (an advantage to Japan worth more than taking Hawaii), but any American counterattack against IJN positions would mean that virtually the entire remaining inventory of USN fleet carriers would be exposed to annihilation against a large airbase network backed by a powerful carrier fleet. If ordered, assembled US forces on the West Coast (the Pacific Fleet bolstered by all heavy units of the Atlantic Fleet) would be capable of relief action by about January 5th or 10th. The objective of a counter-attack would be to suppress the IJN air base network at Kauai, Maui, Molokai and Hawaii while reinforcing Oahu to the point where remaining airbases there could reassert domination of Hawaiian airspace.

USN carrier locations, December 7th, 1941:

Saratoga - San Diego, California.
Hornet - Atlantic Ocean, on shakedown cruise.
Ranger - At sea, returning to Norfolk from Trinidad. Arrives December 8th.
Wasp - Grassy Bay, Bermuda
Yorktown- Norfolk, Virginia
Long Island - Norfolk, Virginia


Carrier......F4....F2.....SBD....SB2U....TBD...SBN......SOC.....SBC
Wasp.......35.....0.........0.........37.........2.......0...........0...........0
Ranger*....35.....0.........0.........25.........3.......0...........0...........0
Yorktown..18.....0........38.........0.........14......0...........0...........0
Hornet......21.....0.........0..........0..........8.......7...........0..........39
Saratoga..10.....0.........43.........0.........12......0...........0...........0
Long Isl.....0......7.........0..........0..........0.......0..........13..........0
Total........119....7........81........62.........39......7..........13.........39
= 367 Aircraft

(types SBN, SOC and SBC were obsolete and ill-suited for combat)

* - Ranger unlikely to see combat service in the Pacific (she might be used as a ferry), but her aircraft could be made available to Hornet.

Pitted against this element of four carriers (Hornet, Yorktown, Wasp, Saratoga), the IJN would have Kido Butai, the light carriers, plus the expanding air base network at Hawaii:

IJN Airbase status, Jan 1st 1942*

Island.......Capacity.........Max on hand
Maui..............85......................47
Molokai..........70.......................0
Kauai.............75......................47
Hawaii............85......................47
Seaplanes................................36
Total..............315...................178**

* - While it is not assumed that Japanese nationals in Hawaii would fight for Japan, it is assumed that the IJA and IJN would have little difficulty in recruiting ample quantities of local Japanese labor for work on expanding captured airfields.

** - In the event of a major USN reinforcements moving to California, the entire Japanese 23rd and 24th Air Flotillas would be available to bolster defenses at Hawaii to over 300 aircraft.




Potential modes of failure in Japanese attack on Oahu.

1) Detection of fleet prior to December 7th.

Probability: Low.

Consequences: No battle at Hawaii. Focus of eastern offensive becomes a luring battle based on the capture of Johnston, Midway, Samoa and Palmyra.

2) Failure to achieve victory during decisive battle of 7th/8th/9th.

Probability: Moderate. (Failure to sink Lexington and Enterprise. Loss or damage of IJN carriers. Weather related difficulties)

Consequences: Cancellation of eastern offensive. 16th, 48th, 2nd I.D. diverted to southern offensive. 7th I.D. withdraws to Marshalls. Fleet returns to Japan.

3) Failure of initial invasion of Oahu by 16th/48th ID.

Probability: Unknown.

Consequences: Extension of Hawaiian campaign beyond two months a certainty. Chances of eventual failure to capture Oahu increased.

4)Failure to defeat USN efforts to reinforce Hawaii after January 1st.

Probability: Low.

Consequences: Either a strategic withdrawal or an escalation of the battle into an all-out test of nation strengths.




Potential modes of failure in an American defeat

1) Elimination of both Lexington and Enterprise without reciprocal loss to the Japanese.

Probability: Substantial

Consequence: Atlantic Fleet carriers would not be considered adequate to the task of tackling Kido Butai or the IJN base network at Hawaii. Europe first orientation will not be reversed.

2) Failure to reverse Rainbow Five focus on Germany.

Probability: High

Consequence: Oahu falls.

3) Failure to prevent fall of Kaneohe and landing of IJA 1st Artillery regiment

Probability: Unknown.

Consequence: Supply of Oahu made more difficult. IJA offensive on Oahu will cause grinding attritional battle requiring great demands for supply. US bases will be pummeled into permanent incapacity.

4) Failure to maintain adequate supplies through blockade or loss of points of import on Oahu.

Consequence: Oahu falls.

5) Loss of Atlantic Fleet carrier striking power to IJN submarines (prowling off West Coast) and/or IJN airpower.

Consequence: Probable loss of Oahu.

Summary: IMO, Japan's chances of conquering Oahu only rise above 50/50 upon achieving victory in the naval battle of December 7th/9th.



Implications of victory.

1) Humanitarian crisis and civil evacuation.

A surrender on Oahu would occur because the garrison would not have access to the supplies and reinforcements needed to continue fighting or feed itself and the civilians of the island. At the point of capitulation, the responsibility for providing supplies to the islanders would shift to the Japanese (naturally, playing on the fear of mass starvation would be a method by which the Japanese could manipulate the garrison into a premature surrender).

Assuming that Oahu would subsequently be transformed into a major IJN base, and assuming that this process meant about 20 transports per month, then space for 30,000 evacuees would be available on the return legs of these vessels (20 x 1,500 each). Further assuming that Hawaii had about 500,000 mouths, but could only feed 125,000 indigenously, then the difference of 375,000 would have to be made up by imports from Japan and tapping into the livestock reserves on the outlying islands. These captured livestock reserves might be good for perhaps 30,000,000 person-days of food by the end of the siege. At a cubic volume of .14 square feet per person per day, Hawaii would require at least 16,000 tons of shipping per month (3 ships) in order to feed 50% of the 375,000 surplus mouths in the territory. With an evacuation program and the livestock, this would suffice to normalize supply/demand in 6 months:


Month....Surplus Pop.......Required..Import.....Livestock
1..............375,000............11.25.....5.625..........26.4
2..............340,500............10.22.....5.625..........21.8
3..............306,000.............9.18......5.625..........18.2
4..............271,500.............8.14......5.625..........15.71
5..............237,000.............7.11......5.625..........14.23
6..............202,500.............6.08......5.625..........13.78

(measured in millions of person-days of food)


Offensive Base.

Even assuming the loss of a number of carriers in the fighting, the combination of Oahu as a forward base and the existence of a striking force capable of using it transforms the dynamics of the Pacific War. Now the United States is forced to maintain an air garrison in California sufficient to defend the entire coast from Seattle to San Diego against fast raiders originating from Hawaii - perhaps 800-900 aircraft badly needed elsewhere. IJN submarines also would have acquired a base far closer to American shipping lanes, allowing the option of a real anti-shipping campaign.

2nd Phase Offensive.

The battle at Hawaii will have diminished the Japanese strategic reserve of oil, in turn forcing 2nd Phase offensive action to secure Java and tighten the ring around Luzon. After a period of recuperation in Japan, Kido Butai would be available for 3rd Phase ops by April or May 1942. In whatever direction is chosen (Indian Ocean, Australia), the primary impediment to Japanese expansion (the United States Navy) will have been removed from the equation, allowing the Japanese greater freedom of choice in their movements, as well as a greater chance of success.

glenn239
Member
Posts: 5590
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

(19) Modelling effects of artillery and aerial bombs

Post by glenn239 » 17 May 2007 16:32

Required is some form of model to predict the effects of various shells and the density of fire needed to achieve a certain measure of damage. The following website provides a good primer on how to gleefully plan to blow the hell out of targets with artillery.

http://members.tripod.com/~nigelef/wt_of_fire.htm



The common denominator there is the British 25lbr artillery shell. The number of 25lbr shells required to inflict 20% damage upon troops in the open within a 100 x 100 yard box on "average" (ie, uneven) ground was 40 rounds. Later, the site also uses 40 rounds as a benchmark for 20% damage on a soft-skinned vehicle. "Average" ground assumes hills and undulations in terrain, like your typical stretch of countryside. Pearl Harbor - and particularly the airfields on it - were optimal targets in this sense. They were not "hilly", and hence the ground was less likely to interfere with the distribution of shell splinters. In addition the most important vehicles targeted would be aircraft, not trucks, and since these were both larger and more vulnerable to damage then effectively the radius of shell effect would expand when employed against them. 20% damage for 40 shells in a hilly box 100 x 100 yards is a useful starting point, since this criteria may understate the effect of shellfire on flat ground, and so builds in a margin to allow for target resistance.

The link also provides information on other types of shells - their weight, HE content and 25 lbr equivalency (how many 25 pounders it takes to equal their effect):

Shell....................HE LBS.........25 lbr Eqv.
76.2mm..................1.526................0.5
25-pdr.....................1.75..................1
3.7 in How...............2.52..................1
10.5-cm GR38.........3.07.................1.3
105mm M1..............4.88.................1.7
122mm....................8.11................2.2
4.5 in.......................3.78................1.5
5.5 in 100lbs.............10..................2.4
5.5 in 80lbs.............11.97...............2.6
15-cm GR42............13.58..............2.8
152mm...................13.82...............2.8
155mm...................15.01...............2.9
7.2 inch...................27.94................4

I've looked at three basic methods to fit other shells and bombs (not in the table) into a universal chart and predict their 25 lbr equivalency. These are:

Effect by weight of HE only.

Ignoring the weight of shell and using only the weight of the explosive filler to predict 25lbr equivalency gives this relationship as a potential solution to fit to the data on the website:

25 pounder shell equivalency = .5872 * HE filler weight ^.604

Effect by weight of shell only.

Ignoring the weight of the HE filler and only going by shell weight gives this equation:

25lbs effectiveness = .917 * Shell Weight^.7439

Prediction by formula.

The formula I'm going to use combines weight and HE characteristics into one value, providing a smoother equivalency-prediction curve than just using the weight of the shell on its own. I don't pretend this is the best fit possible for the data, but it does smooth out the weight bumps and makes a passable prediction for the website data,

25lbr shell equivalency = .1026 * (Shell Weight / Log(HE weight/Shell weight) * -1) ^.6923


Image

In graphing the relationships it looks that a model which uses HE weight more closely predicts the real effectiveness of the shell data given on the site than does one which goes by only by shell weight. For shell weight, invariably those projectiles which have high HE content perform better than predicted, those with lower HE content, worse than predicted. Which seems to suggest weight is a secondary consideration to HE power. For modeling all weapons performance as forms of battlefield artillery I will use weight of HE (with an additional penalty for the poor performance of AP fusing by rating AP explosive content at 1/10th its weight). This approach favors bombs and high HE content artillery over naval shells.

Exception.

Here:

http://www.fischer-tropsch.org/primary_ ... 200-19.pdf

On page 10 is found a chart where the A.A. radius of effect of IJN shells is listed far to the right. Note the IJN 4.7" howitzer shell, which has similar weight (28lbs) and HE characteristics (19%) to the British25lbr. This is used as the substitution for the 25lbr and acts as the necessary link to model the effects the larger IJN shells in comparison to the 25lbr. The site gives us the following maximum A.A. radius of effect for each shell:

18.1": 74.4 yards.
16": 64.1
14": 54.9
8": 32.05
25lbr (subbed for 4.7" howitzer): 18.13

The data curve here suggests that the relative brittleness of aircraft (in comparison to regular land targets) places a greater premium on the total weight of metal flying through the air (fewer, larger slow moving shards are not much worse than more chunks with higher kinetic energy) than is normally the case. Judging by the Technical Mission data, predicting shell effect by HE content alone will understate the effect of shells against unfortified aircraft parked in the open. For measuring anti-aircraft land bombardment effectiveness, I will use the formula above, not just HE content alone.

IJN Shell and bomb effectiveness in 25lbr equivalency.

Type - gun type or bomb weight.
HE - weight of explosive filler in lbs.
25lbr - Number of 25 pounder shells required to duplicate the effect of one shell/bomb.
AP Value - Number of 25 pounder shells required to duplicate AP version of shell.:

IJN weapons

Type....HE....25LBR....AP Value
6.1"......6.8......1.87.........0.18
6".........6.4.......1.8..........0.18
5.5"......6.3......1.78.........0.18
5" BB...4.2......1.39.........0.14
5" (DD).4.86....1.52.........0.15
8".........18.......3.36........0.34
14".......65.1.....7.31........0.73
16".......97.7.....9.34........0.93
18.1"....136.....11.41.......1.14
30kg......31.......4.7
60kg......62.......7.14
250kg...260.....16.88
500kg...522......25.71
800kg...840......34.28



US Weapons

155mm..........2.9
3" HE............0.67
3" AP............None
6" AP............0.22
8" AP............0.45
8" HE...........3.08
240mm HE...6.75
12" AP.........1.12
12" HE.........6.96
14" AP.........1.48
14" HE.........9.59
16" AP.........1.9
16" HE.........12.30


Anti-aircraft ratings:

Type........25lbr Eq.
8"...............4.22
14".............12.58
16".............16.67
18.1"...........21.35
250kg.........17.67
500kg.........28.56
800kg.........39.54



Destructive potential of Japanese weapons platforms.

In the thread, the ratio of AP/HE ammunition aboard ships will be specified. But for determining the max. destructive potential for each IJN weapon system here, it is assumed that all rounds are HE (since AP is of next to no use in land battles except against fortifications).

Surface Ships: Total 25lbr equivalency by weapon type and rounds per gun.

Ship.......Gun....Qty rounds...25lbr....total
Yamato..18.1.....9....100......11.41..10,269
Yamato...6.1.....12...150.......1.87....3,366
Yamato....5.......12...300........1.4.....5,040
Nagato....16.......8.....90........9.34....6,725
Nagato...5(BB)..28....200........1.4.....7,840
Kongo.....14..... 8......90........7.31....5,263
Kongo.......6.....16....150........1.8.....4,320
Kongo....5(BB)...8.....200........1.4.....2,240
Fuso........14.....12.....90.........7.31...7,895
Fuso.........6......16....150........1.8.....4,320
Fuso......5(BB)...8.....200.........1.4.....2,240
Myoko......8......10....122........3.36....4,099
Myoko...5"(BB)..8.....200.........1.4.....2,240
Mogami (Same as Myoko)
Tone.........8.......8.....122........3.36....3,279
Tone......5(BB)...8......200........1.4.....2,240
CL...........5.5"....7.....150.......1.78.....1,869
Kagero..5"(DD)...6.....150.......1.53.....1,602
Asashio.5"(DD)..6.....150.......1.53......1,377
Fubuki...5"(DD)..6.....150.......1.53......1,377

Shokaku
Type......Qty......25lbr..........Total
800kg.....60.....34.28.........2057
500kg....60.....25.71.........1543
250kg...312....16.88..........5267
60kg.....528......7.14..........3770
30kg......48........4.7...........226

Hiryu/Soryu
Type......Qty......25lbr..........Total
800kg....36.......34.28.........1234
500kg...36.......25.71..........926
250kg..240......16.88.........4051
60kg....360........7.14.........2570
30kg....140.........4.7...........658

Akagi
Type......Qty......25lbr..........Total
800kg.....55.....34.28..........1885
500kg....55.....25.71..........1414
250kg...284...16.88...........4794
60kg.....400.....7.14...........2856
30kg.....130......4.7..............611


Kaga
Type......Qty......25lbr..........Total
800kg.....56......34.28........1920
500kg.....56......25.71.........1440
250kg....292.....16.88.........4929
60kg......400.......7.14.........2856
30kg......130.......4.7.............611

Summary

Ship......Qty.......25lbr Equiv..........Total 25lbr value
Yamato...1............18,675..............18,675
Nagato...2.............14,565..............29,130
Fuso......2.............14,455..............28,910
Zuikaku..2.............12,861.............25,722
Kongo....4.............11823..............46,173 (Hiei less 4 x 5")
Kaga......1.............11,755.............11,755
Akagi.....1..............11,560............11,560
Hiryu......2...............9,439............18,878
CA.........8...............6,339.............50,714
Tone......2................5,519.............11,039
CL..........8...............1,869.............14,952
DD........40...............1,377.............55,080

Total fleet firepower equivalent in 25lbr (Max): 322,588

Damage to buildings.

In some cases the firepower potential of various systems will be expressed by damage to buildings. USSBS, Vol10, Chp 2, pg 27 provides probable value of MAE ( Mean area of effect, 1,000 square feet of damaged building per ton of bomb)


500lbs GP 13.3
1000lbs GP 13.0
2000lbs GP 13.9


Building Damage Values by weapon type

Weapon............Sq. Yards expected Damage
800kg bomb..............1195
500kg bomb...............743
250kg bomb...............370
18.1".........................194
16"...........................139
14"...........................92.64
60kg bomb.................89
30kg bomb.................45
8".............................25.62
6.1"...........................9.68
6"..............................9.11
5.5"...........................8.97
5"..(DD).....................5.98
5" (BB)......................6.92

Max. building destructive Sq. yardage, by ship types

Type........Dam Potential.....Qty.........Total
DD.................6,225............40..........249,000
CL..................9,414.............8............75,312
Tone...............34,564...........2............69,128
CA..................40,184..........8............326,512
Kongo............95,392...........4............381,568
Nagato..........109,668..........2............219,336
Fuso..............128,743.........2............257,486
Hiryu..............196,906.........2............393,812
Yamato..........213,120.........1............213,120
Akagi.............253,132.........1............253,132
Kaga.............258,030.........1.............258,030
Shokaku........280,936.........2.............561,872

By Type

CV..................1,466,846
BB..................1,071,510
CA.....................395,640
CL........................75,312
DD.....................249,000
Land base air(1)..126,491
Land base air(2)..192,890

Land base air (1) is all bombs allocated in December. (2) is January.

Determining Probability of hit.

In some cases, such as calculating the odds of putting a shell into a Disappearing Carriage mount, or the odds of hitting an oil tank, the answer will be expressed in terms of percent chance of a positive event:

......................R
Pm = (A-E)/A

Pm = Probability of missing a single target element in the target box
A = total target area or total salvo pattern area
E = area of shell effect or of target size
R = Number of rounds expended.

For example, using the 25lbr shell on the website, solving for E (where A=100 x 100 yards, R = 40 and Pm = .8) gives the 25lbr as having a destructive area of effect of 55.41 yards square. Using the HE based on the Japanese shells derives the equivalent destructive radius for the larger shells.

To measure the effect of a bombardment, I usually will split it into either it's 25lbr equivalency, or rate it according to the total square yardage of building or aircraft damage being delivered. (For example, a Kate bomber with 2 x 250 lbs bombs will drop 640 square yards of building damage/destruction, or 1958 square yards of aircraft damage (25lbr damage area of 55.41 * 250kg equivalency of 17.67 *2 bombs), or 33.76 x 25lbr shells for infantry attack. If the Kate instead comes with a 250kg bomb and 6 x 60kg bombs, then it is good for 904 square yards of building damage, etc.

Total damage carried isn't the whole story though. As more ordnance is dropped into a target zone, some of it will hit in the same spot as previous rounds. To account for this, picture all bombardments as a succession of individual rounds. As each impacts the target zone, some will strike fresh ground, others will overlap into that which has been previously hit. Suppose that at 3am on December 6th Yamato appears off the north shore of Oahu and commences a bombardment of 450 18.1" HE rounds into Shofield Barracks. Let's say Schofield's main barracks and storage area is 300,000 square yards. Yamato's first shell lands, scoring 194 square yards of building damage. Then her second shell comes down. It hits for 193.87 square yards because a small fraction of Yamato's second shell will, on average, overlap the area covered by the first. For few bombs and shells this effect is negligible, but fire in alot of them, and it causes a significant divergence from the total possible damage. Yamato here could score 87,300 square yards of damage, but because of overlap, she should hit for about 76,641 square yards (which is still quite the battering of a 300,000 square yard target!)

glenn239
Member
Posts: 5590
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

(20) Modelling Aerial Attrition

Post by glenn239 » 17 May 2007 16:33

Anti-Aircraft defenses.

American anti-aircraft guns are rated by a formula to determine kill points. Kill points are translated into into A.A. kills according to a number of variables.


A.A. point formula is:

(Rate of Fire * Shell Weight in pounds) + (.5872*Weight HECharge^.604)*100+(Square Root of Slant range in yards)

Values are corrected to where a 50 CAL MG = 1)

Shell info from Navweap site. A.A. Slant range taken from:

http://www.lonesentry.com/manuals/germa ... l_use.html


MG = 500 yards
Light AA = 2000 yards
Heavy AA = 8000* yards


Gun.....ROF....Shell LBS....HE.........Slant.....Points
5"...........15...........54...........7.6.......8000.....18.46
3"...........20...........24..........1.76......4800.....10.63
40mm....120.........4.75.........0.15......2000.....10.36
1"..........100..........1.9.........0.37......1500.......3.97
20mm....290.........0.53........0.24.......910........3.19
50 Cal...200.........0.181.........0..........500.........1

* - Lundstrom credits the 5.5" with a slant range of 10,000 yards

I don't pretend this to be all too accurate, but a 40mm cannon being 10 times better than a 50 Cal MG, and a 20mm 3 times better feels about right, so what the hell.



Determining the naval gun AA Kill Value is taken from the Battle of the Coral Sea and Battle of Midway.

Coral Sea

Ship...........5".....50 Cal.......Qty...........Points
Yorktown....8........40.............1............187.68
Lexington...16.......0..............1.............295.36
CA's...........8........8..............4.............622.72
CA.............4........0..............1.............73.84
DD.............5........4..............7.............674.1
DD.............4........4..............3.............233.52

Total Points: 2087.22
Total AA Kills: 3
Points /Kill: 695

Midway

Ship...........5".....50 Cal.......Qty...........Points
Yorktown....8........40.............1............187.68
CA's...........8.........8..............2............311.36
DD.............4.........4..............5............389.20

Total Points: 1776.48 (2 raids)
Total AA Kills: 2.5
Points /Kill: 710.59

Naval A.A. will be estimated at 700 points = 1 kill.

US Army AA point value

Army A.A. is rated at double the effectiveness of Navy AA (350 points/kill).



Defenses of Oahu, Dec 7th at 7am.

(Vol 23, pg 1455 and Vol 12, 353)

Service............Gun.........Qty...........Points.........Total
On ships...........5.5"........232...........18.46..........4283
On ships.............3".........135...........10.63.........1435
On ships.........40mm.........1.............10.63........10.36
On ships............1.1"........16.............3.97............64
On ships.........50 Cal......397...............1..............397
Marines.............5.5"........10............18.46...........185
Marines.............3"...........12............10.63...........128
Marines...........50 Cal.......58...............1...............58
Army..................3"..........86............10.63...........914
Army...............40mm.......20............10.36...........207
Army...............50 Cal......136..............1..............136
Navy(base)........5.5"..........8.............18.46...........148
Navy(base).........3"...........11............10.63...........117
Navy(base).......50 Cal......20................1...............20

Total Points:

Navy (ships): 6,188 (8.84 kills)
Army: 1,257 (3.59 kills)
USMC: 370 (1.06 kills)
Navy (Base): 285 (.81 kills)

Oahu defenses, total anticipated kills (per wave)


Fleet.........Low.....Med......High
In Port.......14.3....11.47......5.5
At Sea.......5.46.....3.3.......1.65

(Low/Med/High totals are not cumulative - 14.3 AA kills is max expected A.A. losses per attack wave if the IJN attacks all areas of the island. Note that this total exceeds the historical performance by a considerable margin, even allowing for many Army batteries being unready during the attack). Med Alt is 5" and 3" guns only. High altitude is 50% of Med Altitude value.

By this system, had Oahu's AA defenses been fully alert on December 7th, the total losses in the raid would have been 38 aircraft. The A.A. defenses of Oahu were insufficient to protect the island if the fleet were at sea instead of in port.

Area AA of Oahu (Dec 7th deployment) estimated by sector.

Location...............Points...........% of total defense
Wheeler/Sch...........174.......................3%
Ewa........................215.......................4%
Weaver...................161.......................3%
Hickam...................120.......................2%
Navy Yard(Army).....286.......................6%
Marine Defenses.....370.......................7%
Ships in harbor.......3094*....................62%
Alamaneiu..............140.......................3%
Honolulu.................54.........................1%
Kaneohe................108........................2%

* - naval AA value corrected to 350 points/kill.




Air Vs. Air. Summary.

In the past, trying to get anyone to agree as to what a reasonable projection for aerial attrition has proven contentious. Generally speaking, when aircraft enter into combat, 50% of all the pilots engaged will never accomplish anything during that battle, nor during their entire flying careers for that matter. Another 25% or so of the pilots might get a kill - these were the men that got one or two victories during their combat career, but otherwise filled a place on the roster. About 20% of the pilots did 80% of the damage.

Summary of selected historical actions

Action.........Zeros..Effect..Kills..Leth...F2/F4F...Kills...Leth
Coral Sea......18.......18.....12....0.67......20.........7......0.35
Yorktown(1).....4........2.......1.....0.25.....17........14.....0.82
Yorktown(2).....6........6.......4.....0.67.....16........6.5....0.41
Midway Isl.....36.......36......15....0.41.....25........11.....0.40

(SBD lethality at Coral Sea - 23 on hand, 6 kills, .26 kills per plane)

Effect = effective total of Zeros in engagement.
Leth = Lethality in kills per fighter during the battle.

The most important Zero variables look to be whether the fighters were fresh (ie, had full loads of 20mm ammunition), and whether they outnumbered their opponents.

Action....Ratio Zero/Defenders....Zero lethality......Allied (fighters only)
Coral.............0.42 to 1........................0.67.......................0.35
Yorktown(1)...0.12 to 1........................0.25.......................0.82
Yorktown(2)...0.37 to 1........................0.67.......................0.41
Midway Isl....1.38 to 1.........................0.41.......................0.44

USN fighter lethality appears more to be determined by the ratio of Zeros to Allied Fighters. So I'm going with that. Formula for USN/USAAF fighter kills is:

Image

Lethality per aircraft = 0.2009 * (Ratio of Zeros to US fighters) ^ -.661

USN SBD CAP lethality, (also A5M4, P-36, P-26) is:

Lethality per aircraft = .1324 * (Ratio of Zeros to SBD's) ^ -.6537

Zero Lethality -

If outnumbered by defenders then it's .6
If outnumbering defenders, then it's .35

Prediction vs. Reality.

Here's how this model stacks up against real life:

Battle...........IJN Prd.....Act kills......USN Prd.....Act kills
Coral Sea........11...............12.............12.43...........13
Yorktown(1).....2.4..............1................8.89............14
Yorktown(2).....3.6..............4................6.15............6.5
Midway...........12.6............15..............3.94............11
Ceylon............21.6............19...............9.34............7
Trincomalee....13.3..............9...............3.31............0?
Darwin.............10...............9...............0.86............1?

Two anomalies stand out in this list where predicted results vary significantly from real results - Yorktown(1) and Midway. With the first, when attacking Yorktown and in what had to be one of the worst non-Nagumo decisions of the day, Kobayashi's escort peeled off and engaged USN SBD's that posed no immediate threat to Hiryu. They did not return until Kobayashi was already under attack, and when they did arrive, they probably were short of much or all of their original 20mm ammunition. Without this, the Zero was nothing more than the A5M4 Claude's prettier sister.

If we adjust for the late arrival and presumed lack of 20mm by rating Kobayashi's escort as effectively 2 x Zero, then the prediction for Yorktown (1) becomes: IJN Kills: 1.3 USN kills: 14, which is bang-on. Note then, that according to this speculation, Kobayashi's ill-considered decision not only cost him his life, but also about 5 more live drops on Yorktown (= 5.66 expected bomb hits on the carrier instead of 3). If that had happened, Tomonaga strike - which could have been the most competent small-unit attacks ever delivered by IJN aircraft in WW2 - almost certainly fall onto TF16 instead.

This leaves the Midway Island anomaly - expected kills by USMC fighters against 36 Zeros were only 4, but real kills totaled 11. What can be said? They were Marines. This will be handled by the following rule: Regardless of the Zero/USN cap ratio, USN/USMC/P-40 fighter lethality vs. mixed IJN formations is never less than the .35 ratio of Coral Sea.

(It is noted that the Marine PK at Midway had much to do with the fact that the Zero escorts for the most part failed to break up the attacks prior to their reaching the bomber formations, and in part due to Marine air controllers succeeding in getting their charges into attack positions). For Tinkerbell, it is simply assumed that both of these things will happen).

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Post by ChristopherPerrien » 17 May 2007 22:13

Hi Glen,

An interesting piece of work, I have only had time to read the first page so far and not checked a few matters I have problems with , currently the only two things that spring out at me are:

1. noted2. Your comments/conclusions about IJN airstrikes directly damaging the coastal batteries and defenses of Wake island are in error. The damage to those batteries was the result of the shock and sypathetic detonation of ammo around these batteries CAUSED by the detonation of a large store of dynamite in a shed. A big shed, I guess, 125 tons of dynamite, IIRC. I wonder if the crater is still there. Granted the Japanese aircraft bombed/shot-up? this shed, but that is not the same as them bombing coastal batteries/fortifications intentionally. So this is not an applicable example.

BTW- I like the inclusion of the surf tables around Oahu, no wonder surfers talk about them in awe so much. You'd have to be a master boat handler to put a landing craft on most of those shores, most days, without "wiping out" i.e. broaching/beaching, and it would play hell with an amphibious landing and subsequent support if not totally and fatally screwing it up. The landing Japanese soldiers had better all know how to swim.

I will move this post in the future, if you plan on posting more stuff, looks pretty good so far, I commend your work.
Last edited by ChristopherPerrien on 20 May 2007 18:29, edited 1 time in total.

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Post by glenn239 » 17 May 2007 23:40

Chris,

Thanks for the feedback. "Totally gay", as in, "blocking the entrance to the harbor is a totally gay strategy" means that the plotters of such a move would have to conduct themselves with a disconnected sense of joyous levity in order to arrive at the conclusion such a move was a feasible method by which to barr the US Pacific Fleet from obtaining access to the Pacific Ocean.

The purpose of the post here is for a final fact-checking session prior to posting on another site. Since this is still a work in progress, I'll be making changes anyway and will accomodate your request within days. (I've noticed a few errors already that need to be changed).

Re: Wake Island. I'll modify the entry to account for this fact - can you post a source I can link? Also - note that with respect to General Short's assessment of Batteries Hatch and Williston in the Coastal Defenses section, a big problem was that both these positions had large numbers of propellant charges near the batteries in storage which could not withstand a bomb hit. This was very dangerous state of affairs, and is along the lines of the problem you describe at Wake taking out both the 3" and 5" guns.

With respect to Oahu's surf, your impression of it's danger to the attacker is true with respect to the north shore and, at many times during the winter, the west shore. These could get crazy enough that no landing could occur for days on end. The south and east shores were more consistent and friendlier from an invader's standpoint.

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Post by Eugen Pinak » 18 May 2007 16:21

glenn239 - What can I say - I'm impressed. You're one of the few alternate historians I know, who bother themselves with such a detailed work on their alternatives.

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Post by glenn239 » 18 May 2007 23:35

Thanks. This thing is an attempt to devise a universal model to predict AH options for the Pacific War in general as much as it is looking at the dynamics of an Oahu campaign. Anyone out there with info on IJN/IJA shell inventory levels in December 1941?

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Post by ChristopherPerrien » 20 May 2007 19:28

glenn239 wrote:Chris,


Re: Wake Island. I'll modify the entry to account for this fact - can you post a source I can link? Also - note that with respect to General Short's assessment of Batteries Hatch and Williston in the Coastal Defenses section, a big problem was that both these positions had large numbers of propellant charges near the batteries in storage which could not withstand a bomb hit. This was very dangerous state of affairs, and is along the lines of the problem you describe at Wake taking out both the 3" and 5" guns.

.
My earlier post was slightly in error. The shed had 125 tons of dynamite and caused damage to the range finders of the 5in battery and damaged some of the 3in guns. The raid occurred on the 9th of Dec and was actually done by long range Nell bombers from Roi-Namur, not carrier planes. Even with this the 5in were not knocked out of action and later engaged the enemy landing fleet destroying 1 DD and damaging 2 along with the light cruiser Yubari.

The carrier plane attacks later around the 21-22 Dec did atack around the batteries and did cause some non-effectual damage but definitely did cause those batteries to be "suppressed" for awhile to an extent. When the landing occured later, the batteries were not in the action, which I note was done in darkness and apparently was not in the field of fire for these batteries. I think by that time there was only one damaged searchlight left on Wake. Its been awhile since I have really read up on the battle.

An excellent link and although I only scanned through it is http://www.ibiblio.org/hyperwar/USMC/USMC-C-Wake.html

Last account I read of Wake was in a book "Last Stand " by Geoffery? Perret , and mentioned the dynamite explosion, the hyperwar link mentions it too. I have seen others that contain more detail about the battle, but the Hyperwar link is probably the best to work with.

Personally I feel Devereaux could have held Wake , but on the day of the surrender he had thought the Japanese had already taken the other side of the atoll. In that, he was mistaken because of the lack of communications. If he had known that," Wilkes island"? had effectively destroyed the landing there , he could have beaten the Japnese that were left facing his forces on Wake.

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Post by glenn239 » 20 May 2007 21:05

Thanks for the update. The account from Wake Island indicates the Val damage to the batteries of Wilkes Island was not cosmetic, but rather rendered them beyond repair (at least immediate repair).

I don't think Wake could have been held - the Japanese had a tremendous firepower advantage and outnumbered the defenders. The battle might have gone on for a while longer, but the issue wasn't in doubt. It might be the case that a timely surrender prevented atrocities on the Japanese side.

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Post by ChristopherPerrien » 20 May 2007 22:15

glenn239 wrote:. It might be the case that a timely surrender prevented atrocities on the Japanese side.
8O Are you kidding? Most of the Marines captured never made it home. And all the contractors(400 US civilians IIRC) kept on the island by the Japanese were later murdered.

It is was a decisive factor in several Japanese successes early in the war that American troops thought they were fighting an honorable enemy , because if they had known how utterly callous and sadistic the Japanese treated all non-japanese humans especially POW's, they would have all gone down fighting and perhaps beaten those Japanese in a few earlier battles.

But we digress, I will try to read the second page of your topic soon and perhaps go back and look at some things a little more closely this week.

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Wake book - "A Magnificent Fight" by Cressman &

Post by robdab » 21 May 2007 00:49

Chris,
I agree that your URL, http://www.ibiblio.org/hyperwar/USMC/USMC-C-Wake.html is a good one I would like to point out that the web summary is nowhere near as good/detailed as the actual tome. Try to find a copy on ebay or via inter-library loan if you can. A wealth of information can be found in Cressman's writings.



Glenn/Chris,
I know that you don't want to get into it during discussions of your full Oahu invasion plan, "Operation Tinkerbell" but perhaps THIS is the forum that could be used to more fully discuss the possibility of the Japanese using a blockship to "cork up" the Pearl Harbor ship channel on Dec.7'41 ? I gather from your brief discussion with Chris, just above, that you think it highly unlikely but as you know, I feel otherwise. And so did the US military commanders of the day since this possibility figured prominently in the defensive plans while the expectation of carrier launched air raids was highly discounted.
It seems unfair/unwise to just ignore such an easy tactic from the Japanese "playbook" ?

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Post by glenn239 » 21 May 2007 16:21

A blockship is ignored, at least in the early going. I suppose that it could be argued that a Maru could be specially adapted to the role with some armor and such, but it just doesn't seem that interesting from a pseudo-historical perspective, since the argument would rapidly de-evolve into a "yes they could - no they couldn't" exchange that would absorb bandwidth from any number of more interesting Hawaii invasion topics.

If the IJN could sail a blockship into the channel entrance and sink it at the right point of the harbor mouth, while under fire from every gun in the area (it would be attacked by USS Ward and any manned guns as soon as it entered the restricted zone), then yes, the USN would be in deep ka-ka. At that point, and assuming that the air attacks go off without a hitch, the only thing separating the USN from disaster at the hands of the Main Body would be batteries Williston and Hatch, neither of which I'd give much chance vs. a Kido Butai strike.

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Post by ChristopherPerrien » 22 May 2007 06:03

This is all nice work, but by reading through it , I have realized that the operation is simply too big to have any chance of suprise and without suprise it has no chance of success. This is probably why Yamato was never noted to have proposed such an operation before the war or that there was no serious debate on it. This lack of suprise would have been become readily apparent in any staff excersise.


The US gov knew we would be at war with Japan by no later mid 1942 and was planning for the war to happen. Using the "known" historic capabilties of US Sigint and Humint at the time , this HUGE operation would have revealed itself, and while Comint in the form of breaking the JN-25 code was only 10% at the time of Pearl Harbor(or so they say :wink: ), other codes the Japnese military were using were being readily broken before Pearl Harbor. This operation would have been TOO BIG and NOISY to hide.

In the real war, the Allies KNEW there were invasion convoys assembled and when they headed towards Malaysia and the Phillipines. These convoys were far smaller than the fleet assembled for this operation and they were known about beforehand. In the few days the Malaya invasion fleet was at sea, Roosevelt ordered a US flagged ship( the Isabel, PY-10) to attempt to encounter them in hopes of having a pre-emptive reason to start the war.

The only reason the 1st Airfleet managed to sneak to within striking distance of Hawaii, was that it was one cohesive fleet unit of only(10) major warships, and had been almost constantly at sea for the year preceeding the Pearl Harbor Strike, and it used total radio silence, and very importantly, it had no large fleet train behind it or supporting it. If you mobilize most Japanese fleet units especially the BB's that didn't go anywhere without a good reason, and then several army divisions and then enough shipping and supplies to mount this operation the Allies would have a good idea of it occuring and the forces involved, very probably long before the ships set sailed and defintely when it set sailed from the numerous ports needed to mount it , given the known historical example of the Malaya/PI Convoys.

No deception plan would have worked. No-one would haved believed the Japnese would be using their entire fleet for a "training exercise" especially considering the oil embargo they were under at the time. Where else would/could a fleet this size be heading to in the middle of the Pacific, at the time? California? :lol:


So while it is an interesting scenario, it is a big white elephant in a small room.
Don't mean to detract from your work Glen, and while it looks good in some operational/tactical aspects and the details are excellent, it fails on the most basic element to all successful military operations , the element of suprise.

Chris

A note for the "war-game" aspect.

Why bomb the oil tanks( and some other really useful things- navy yard, etc.) if you plan on quickly taking over Oahu? Seems like ALOT of oil that you(insert appropriate WWII derisive slang terms) could dam sure use later. In many ops the Japanese counted on seizing even just food to support their ops. I would do my "bestus" to seize the oil tanks and the oil in them, intact instead of blowing/burning them/it up :idea:

The same can be said for even attempting to block up Pearl Harbor, you need that fine harbor later. Bad idea.

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