Dec.7'41: A Day That Nobody Bombed Panama !

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Dec.7'41: A Day That Nobody Bombed Panama !

#1

Post by robdab » 11 Jan 2009, 21:59

Gents,

WHAT IF the Japanese had knocked out the Panama Canal on Dec.7'41 ?

I believe that they might have done so at little cost and the following is my alternative timeline (ATL) scenario as to how they might have accomplished that feat at the same time as the original timeline (OTL) historical Pearl harbor air raids were going on. It is my hope that discussion generated here will prove to be entertaining (and educational) for all involved.

I'm not suggesting complete or permanent destruction, just a large reduction in the size of vessels able to use that transit shortcut between December 1941 and June +/- 1942. My tiny Japanese ATL attack would attempt to drain the rainwater stored by the Canal system for it's own use during the annual Dec.- April Panama dry season.

One source, http://www.history.army.mil/books/wwii/ ... s/ch12.htm indicates that, "Plans for protecting the Canal against sabotage during an international crisis of this sort had been drawn up in Panama and given constant study ever since the spring of 1936. Now, steps to put them into effect were quickly taken. Three basic measures had been provided for: first, the installation and operation of special equipment in the lock chambers, designed to detect underwater mines and bombs and to prevent damage from this cause; second, the restriction of commercial traffic to one side of the dual locks; and third, the inspection of all ships before they entered the Canal and the placing of (2-25) armed guards on vessels while in transit through it. These measures were instituted between 26 August, when the President gave Secretary Harry H. Woodring the signal to go ahead, and 1 September."

Page #48 of http://books.google.ca/books?id=8WJJGyf ... t#PPA48,M1 does also indicate that US ship inspectors at the Panama Canal began tossing hydrogen cyanide gas into ship's holds in order to fumigate same, in 1923. This makes it far less likely, IMO, that the Japanese or indeed anyone else, would be foolish enough to attempt any "Trojan Horse" type freighter attack on the Canal.

Thus I would expect that the chances of blockship sabotage success there would be very unlikely.

The ATL Japanese surprise air attack that I have in mind instead would see just 3 H6K 4-engined "Mavis" flyingboats trundling in the 855 nautical miles from the Galapagos Islands on the afternoon of Dec.7'41, timed to match with the OTL strike on Oahu. I'm not proposing bombing Panama, I'd torpedo it instead.

Sneaking a pre-war IJN surface warship or two across the busiest shipping lanes of the wide Pacific, un-noticed a la the Kido Butai, would most likely be impossible even in peacetime so a "show-the-flag" state visit voyage by the IJN seaplane tender Chitose would have to provide a peacetime cover story to get those 3 flyingboats within air range of Panama. With official permission from the governments of the countries scheduled to be visited, naturally.

Page #118 of http://books.google.ca/books?id=ehda-fB ... &ct=result details some of the 1940 trade successes that Japan achieved with Latin and South American nations. My ATL suggests that part of the OTL barter deal signed with Argentina might have included the 1941 provision by Japan of long-ranged Mavis flyingboats for the Argentine military. That elongated nation had much isolated ocean coastline to patrol afterall.

A triple Mavis delivery by Chitose would thus be easily justified and would not be expected to pass anywhere near the Panama Canal.

What world power would be greatly worried about 1 lone seaplane tender on an announced flyingboat delivery mission many miles away from it's outposts ? Completely un-announced in the newspapers would be a detached fast IJN crewed tanker and Chitose's close escort of 3 IJN submarines, each capable of 21 knots on the surface.

Chitose's OTL war assignment at Mindanao, PI could be fulfilled by the Japanese CVL Hosho, itself detached from the mostly idle Combined Fleet which still had a second light carrier attached to provide it's battleships with CAP services.

Much as was done historically with the Tatsuta Maru's fake voyage thru Honolulu (see Prange's "At Dawn We Slept") Chitose's schedule of South American ports of call visits would be published in various newspapers by the local Japanese consulates but she would never arrive there in my scenario. If spotted by US/UK/Dutch forces on her way across the still peacetime Pacific prior to Dec.7'41, she would merely be reported as being on course and schedule for those announced port visits. She would never even cross the 300 mile boundary of the US Neutrality Patrol zone which extended out from the coasts of Latin and South America. On the evening of Dec.6'41 she (and her 3 IJN submarine escort) would quietly anchor instead in a deserted lee bay somewhere in the numerous Galapagos Islands, which were owned by Ecuador. That South American nation had a substantial Japanese population in 1941, many of whom were fishermen or guano miners out on the Galapagos. Both being good covers for the pre-war scouting of a suitable anchorage for Chitose and her 3 big new flyingboats.

Chitose was originally built to handle 25 single engined seaplanes with 4 catapults and 5 cranes as per the painting to be seen at http://www.combinedfleet.com/chitosesp_t.htm so In order to hoist a much heavier/larger 4 engined Mavis aboard at least one of those midship cranes would have needed to be upgraded to one similar to that installed on the stern of the much smaller Akitsushima as seen at http://www.aeronautic.dk/Warship%20Akitsushima.htm

All 3 Mavis flyingboats would be hoisted over the side during the night, checked out, fueled and armed with twin "shallow water" torpedoes of the same newly perfected type as soon to be used by the Kido Butai for their air attack on Pearl Harbor. After a calm open water takeoff all three would depart at different speeds and on differing courses, for Panama. The reason for those seperate but co-ordinated flight approaches to Panama being the more than passing resemblance of the Mavis to the Pan-American Airline's "China Clipper" aircraft, the Sikorsky S-42. If pre-painted in Pan-Am's minimal colors and markings, any observer expecting to see a lone "China Clipper" pass by overhead could certainly mistake a single Mavis for one of them instead. By no coincidence at all, Pan-Am was flying a daily "China Clipper" shuttle service on the Miami - Cuba - Costa Rica - Panama - Columbia - Venezuela - Buenos Aries route at the time. As well as developing a trans-Pacific route to the Galapagos Islands at the request of the American government.

Please compare for yourself at http://www.warbirdphotographs.com/NavyJB&W/H6K-8s.jpg and http://www.flyingclippers.com/S42.html . Both with 4 engines and twin tails.

Each Mavis could carry a pair of torpedoes as per http://www.warbirdphotographs.com/NavyJB&W/H6K-1.jpg with the "shallow water" wooden tail fins giving a framework for the attachment of a rounded breakaway "fuel tank" end cap added over the torpedo propellers to help with their appearance as long ranged PanAm China Clippers.

The target of those 3 Mavises being the Gatun Dam's (not the Gatun Locks) spillway gates which controlled the water level in man-made Gatun Lake and thus, the operation of the entire Panama Canal.

The Gatun Dam itself, an armored earthfill structure is far too thick to be affected by a torpedo warhead but the same cannot be said wrt the central spillway gates. Only about 8 of the Dam's 14 steel spillway gates could be targeted by air dropped torpedoes because as http://www.panoramio.com/photo/5294557 shows, that curving spillway structure (to the upper left of the photo with the Gatun Locks being seen to the upper right of that photo) is in a somewhat screened position. Each of the 14 electrically raised steel spillway gates were 45' wide by 20' high and made of 1/2" thick plate. Photos of the underwater damage done by Japanese aerial torpedoes to a US battleship at OTL Pearl Harbor leave no doubt that just one torpedo hit would easily destroy each much weaker spillway gate. Please see http://owensarchive.com/world-war-ii/pe ... d_104.html

It is NOT a photo of the Gatun Dam spillway but if you would go to http://www.pbs.org/wgbh/buildingbig/won ... 2_dam.html you will see the closest detailed photo that I could find. The lightweight, thin, unbraced nature of the steel gate is shown, as are the still attached lifting chains that would have raised and lowered the gate had it's left side anchoring rail not failed just before this 1995 photo was taken.

If that volume of water is coming thru with the gate still partially in place, just imagine the current and flow volume if the gate was blown right off ? Other sources indicate that the entire Gatun spillway could drain 144,000 ft3/second thru it's 14 gates so we can estimate 10,000 ft3/sec thru each destroyed gate. Page #190 of http://books.google.ca/books?id=lob2zvf ... 1-PA190,M1 lists a water flow speed thru an open Gatun spillway gate at 43 ft/sec or approx. 30 mph. It would be extremely difficult to conduct repair operations in such a flow.

Certainly the US was aware of the vulnerability of the Gatun Dam spillway to BOMBING as early as 1923 when a training exercise called Fleet Problem I, which is documented at http://en.wikipedia.org/wiki/Fleet_P..._note-Wright-1 , pointed that out quite dramatically.

The questions is what, if anything, did they do about it ? I suspect little as the US defenders of Dec.6'41 Panama did NOT know that the Japanese had perfected a shallow drop depth aerial torpedo and thus would not have been likely to protect against such, just as the OTL at Pearl Harbor illustrates. AA guns may have been deployed at the then peacetime Gatun Dam (but I have yet to find any confirmation of that) however they would be placed so as to protect against overhead bombing, not torpedo drops from some distance away, well out over Gatun Lake.

I do know that 3 US interceptor squadrons, each of 10 x P-36 fighters, were flying in Panama's rainy season cloudy skies already but AFAIK the 71 more modern P-40s which had just arrived were not operational there until well after Dec.7'41.

I have also found several sources which do NOT present the other OTL American defences in a good light:

For example, page #349 of http://www.history.army.mil/books/wwii/ ... s/ch13.htm summarizes the state of Dec.'41 US defences at Panama against a surprise air attack: "He did, however, call to the attention of the War Department certain deficiencies in the defenses of the Canal. In General Andrews' opinion, the commandant of the naval district did not have enough planes or vessels under his control to conduct an adequate reconnaissance. The Aircraft Warning Service in the theater, he reported, was totally inadequate in personnel to supervise the installation of detectors on hand as well as to man the equipment when installed. Only two radar detectors were installed and in operation in the Panama Canal Department. The harbor defenses had less than one complete manning detail available. The antiaircraft artillery had insufficient personnel to man the armament being installed in the Canal Zone and only enough ammunition for one minute of fire per gun for the 37-mm. guns. There were no barrage balloons. The Air Force,General Andrews continued, was totally lacking in night pursuit planes and in very-high-frequency radio equipment with which to direct pursuit in air. Only 8 modern long-range B-17C bombers and 12 modern AC-20 light bombers were available..."

One minute worth of AA fire hardly inspires any confidence that a surprise IJN air attack could be prevented from reaching good positions to launch unexpected torpedo attack on the Gatun Dam's spillway. The US Army itself estimated that loss of all of the water stored in Gatun Lake would have prevented all Canal operations for a period of at least two years and possibly three, depending on the refill rates dictated solely by local rainfall amounts. Sadly this ATL attack scenario cannot possibly drain all of the Canal's water reserves as the Gatun Dam itself would not be split open and exposed to erosion.

Page #274 on http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-8.html provides the assertion of: "The problems involved in providing a serviceable radar screen to alert the inner defenses of the Canal were less easily solved. Equipment in use at these stations was "inadequate" for early warning and "quite useless" for purposes of controlled interception. Sites had been selected for four British-type radars, the sets to be supplied from Canadian production, but improvement in equipment could not overcome deficiencies of operating personnel. Operators in Panama were largely untrained, had been given no indoctrination in the need for precision standards, and were frequently unenthusiastic about their assignment. Radar crews had made no effort to plot the permanent echoes in their search areas, and therefore could not discriminate between such "echoes" and "live" targets. The combination of inadequate equipment, poor site selection, and untrained operators produced such inefficiency that even the best station in Panama was "far below any acceptable standard of operational utility." The elimination of all the deficiencies noted depended on action by the War Department to provide improved equipment and better trained crews. No complete remedy was available to local commanders."

Since they had no OTL knowledge of the American radars, let alone of their deficientcies, my ATL Japanese make no provision to defeat detection by it in this Panama scenario. Fortuneately for my scenario, it seems that those same OTL radars would not likely have posed much of a detection/interception threat to my 3 ATL flyingboats anyway. Being of the same type of air warning radar as installed on Oahu, the one US radar set facing the Pacific Ocean would also have suffered from the same 20 mile minimum "blindspot" experienced by those Hawaiian radars.

Pages #424-426 of http://www.history.army.mil/books/wwii/ ... s/ch16.htm provide: "Although General Andrews recognized the U-boat campaign as "a definite menace to our war effort," he considered the canal to be "the one real enemy objective" and its protection to be his "paramount mission." Although he was somewhat concerned about the possibility of German surface raiders penetrating [from] the Caribbean, he was more than ever convinced that the principal threat was by carrier-borne aircraft from the Pacific.

The means for detecting an enemy carrier force before it launched its planes and for sighting the enemy planes before they reached the canal were the nerve center of the Panama defenses. Patrol planes, operating at about the 900-mile radius, were depended upon for the initial warning of an enemy's approach. Long-range radar (the SCR-271 and its mobile version, the SCR-270) was relied upon for the detection of enemy planes at distances up to about 150 miles. Still closer-in, the fixed antiaircraft defenses relied upon short-range, height-finding radar (SCR-268) for searchlight and fire control.

AFAIK there were only 12 PBY scouts assigned to search the Pacific to the west of Panama out of the 96 that were estimated to be able to provide a proper long ranged search.

At the time of the Pearl Harbor attack however, serious deficiencies existed in the warning and detection system. There were not enough planes and operating bases to carry out the search as planned. There were only two SCR-271 radars in operation, one at each end of the Canal. Although three additional sets arrived by the end of December and were being installed on the Pacific side of the Isthmus, the work was slowed down by a shortage of trained radar engineers and mechanics.

There were nevertheless certain deficiencies which were not entirely the result of a shortage of equipment and trained men. Tests in Panama repeatedly disclosed that low-flying planes approaching directly over the Bay of Panama were not detected by the radar system. Visiting British experts had noted this characteristic in American sets and attributed it to a basic defect of the equipment, but the Signal Corps insisted that, properly placed and operated by competent crews, the American equipment in this respect was just as good as, if not better than, the British radar. Whatever the cause, the blind spot remained. Furthermore, neither the SCR-270 nor the SCR-271 was designed to show the elevation of the approaching plane, and neither gave a continuous tracking plot. These qualities were indispensable for ground-controlled interception (GCI), which British experience had demonstrated to be the most successful method for conducting an air defense."

Pages #160-166 of: http://www.ibiblio.org/hyperwar/AAF/I/AAF-I-5.html detail the poor overall situation in Panama: "The vital importance of this phase of Canal defense was revealed in an estimate of enemy capabilities prepared by the Caribbean Defense Command in the latter part of November 1941. Japan was regarded in respect to the Canal itself as the primary potential enemy, and a carrier-based attack from the Pacific was considered "not an improbable feat." Other possibilities were taken into account, but it was concluded that in any event the most important defensive measure was "increasing and thorough reconnaissance and observation of the air, sea, and land approaches to the Canal Zone." Existing forces in the area were regarded as sufficient to repel any probable initial attack on the Canal provided they were given "timely warning" of the approach of hostile forces. The inability of defending naval and military air forces to perform the required amount of reconnaissance and to provide the "timely warning" constituted perhaps the chief weakness in the defenses immediately prior to American entry into the war. It was a weakness which was recognized by both Army and Navy commanders, their expressed hope lay in the postponement of attack by an enemy until the defending forces could achieve the proper degree of co-ordination and the necessary equipment for complete coverage of the vast sea frontiers."

THUS IT IS REVEALED THAT THE PRIMARY US PACIFIC DEFENSE OF THE PANAMA CANAL IN DECEMBER 1941 RELIED SOLELY ON THEIR MERE HOPE THAT THE JAPANESE WOULD NOT ATTACK THEM ANYTIME SOON !!!

Just how pathetic was that ?

Had the Japanese but known ... or dared ...

Your thoughts & constructive criticisms (with sources), please.



Veni, Vidi, Velcro. - I came, I saw, I Stuck Around

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Tim Smith
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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#2

Post by Tim Smith » 11 Jan 2009, 22:52

Very impressive work. Kind of like a Japanese version of the British Dam Busters raid in 1942.

Two differences: The British raid had 19 Lancasters, here the Japanese only have 3 Mavis aircraft. However the Japanese are likely to achieve surprise, while the British could not. And the Panama Canal is a far easier target in terms of the precision flying required by the strike aircraft.

Even so, only 3 aircraft leaves absolutely no room for error (missing the target), no room for technical problems, and no room for potential casualties prior to weapons release. Everything must go perfectly for the raid to succeed.

The P-36 fighters are a potent threat to the Mavis if even one squadron intercepts, because the odds will be 3 to 1. At best. Worst case, 9 to 1. The P-36 is slow, but a lot faster than the Mavis. So surprise is absolutely vital.

I'd say the raid has a good chance of moderate success. Cracking one gate is almost certain if there is no interception before weapons release, two is likely, three is probable. More than three rather unlikely.

It's just as well the Mavis carries two torpedoes - multiple runs may be necessary.

If successful in putting the Panama Canal out of action for six months (although three is more likely), it will be very difficult for the US Atlantic Fleet to reinforce the Pacific Fleet. In particular the US carriers Yorktown and Hornet will be delayed in reaching the Pacific. Possibly by around two or three months, as the ships will need to sail right round South America. And they'll need a brief refit after they arrive, after such a long voyage.

So the US fleet will be weakened in the first four months of 1942. Operations affected will be the Doolittle Raid on Tokyo, or the Battle of Coral Sea. Basically, being two carriers short, the US will have to choose between the Doolittle Raid or the Battle of Coral Sea. It's one operation or the other, not both, as both operations require two carriers.

So - hit Tokyo and gain a huge boost in US civilian morale, and quite possibly lose Port Moresby and the whole of New Guinea. Or save Port Moresby, but miss a chance to strike at Japan. Personally I think saving Port Moresby is far more important. The Doolittle Raid can wait until after the Battle of Midway. However Roosevelt might disagree....

As far as the crucial Battle of Midway is concerned, that should be unaffected (from the US side) since six months is more than enough time to transfer Yorktown and Hornet from the Atlantic to the Pacific, even with the Panama Canal out of operation.

However - if Roosevelt is stupid enough to insist on the Doolittle Raid, even though that means abandoning Port Moresby, then that means no Battle of Coral Sea. And no Battle of Coral Sea means that the Japanese carriers Shokaku and Zuikaku will not be damaged or plane-depleted, and thus will be available for the Battle of Midway. Kido Butai will have SIX carriers for Operation MI, instead of four. Although the US will have four carriers instead of three, since Lexington won't be sunk at Coral Sea. (Oh, and Yorktown - actually, Enterprise in this timeline - won't be damaged and won't need to be repaired in 3 days.) So the Battle of Midway would be even more hard-fought than historically. Assuming Roosevelt insists on the Doolittle Raid taking absolute #1 priority over everything else.
Last edited by Tim Smith on 11 Jan 2009, 23:19, edited 2 times in total.


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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#3

Post by phylo_roadking » 11 Jan 2009, 23:08

It's ALSO going to get right up Ernie King's nose :lol: for, he'll have no option under pressure from FDR but to deploy smaller surface units in the Atlantic in support of the RN in the meantime, rather than send them round the Horn...which was anathema to him!!!

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#4

Post by Carl Schwamberger » 12 Jan 2009, 04:04

Tim Smith wrote:
If successful in putting the Panama Canal out of action for six months (although three is more likely), it will be very difficult for the US Atlantic Fleet to reinforce the Pacific Fleet. In particular the US carriers Yorktown and Hornet will be delayed in reaching the Pacific. Possibly by around two or three months, as the ships will need to sail right round South America. And they'll need a brief refit after they arrive, after such a long voyage.
Two or three months?? A rough scale off my globe shows a approximate addition of 12000 nautical miles to round Terra del Fuego & return northto 7deg lattitude west of Clipperton island, & pick up the same general course from Pananma to Hawaii. At a stately crusing speed of 20 knots thats about 25 days, a rather ordinary time at sea.

I cant recall the exact time but during one of the Spanish war panics of the 1890s the US crusier Olympia managed coast to coast in about a month. Slower paced British freight ships took a full month to circle Africa from the Central Atlantic to Suez while the Mediterrainian route was closed 1940-43. That measures out similar to the extra distance to circle South America.

I cant see a delay of three, or even two months. In any case the events you mention, the Tokyo Raid and the Coral Sea battle are some four & five months after the Pananma Cannal is closed. This does not add up. Particularly since a sensible course would be to transfer the ships sooner due to the longer transit time.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#5

Post by Tim Smith » 12 Jan 2009, 12:08

My estimate included refit and resupply time in San Diego, plus the time to takes to reach Oahu. Also I'd put a stately cruising speed as 16 knots for fuel-economy reasons (that's half speed for a Yorktown-class carrier.) Still, I might have been a bit off.

Yorktown sailed from Norfolk on 16 December 1941 - so that's almost immediately after the outbreak of war, allowing for resupply time and maintenance check.

Hornet was undergoing refit in Dec-41/Jan-42 to upgrade her AA defences, she had to replace her ultra-short-range (spitting-distance) 24 x .50 cal mgs with short range 30 x 20mm Oerliken cannon. Also she was being prepared for the Doolittle Raid, and left Norfolk with the B-25s already on board.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#6

Post by robdab » 12 Jan 2009, 22:59

Tim Smith, in response to your posting,

Very impressive work. - Many thanks.

Even so, only 3 aircraft leaves absolutely no room for error (missing the target), no room for technical problems, and no room for potential casualties prior to weapons release. Everything must go perfectly for the raid to succeed. - Granted that my ATL scenario is a shoestring effort. The chance of Pearl Harbor being alerted if this Panama raid were discovered early lead me to keeping it as small as was possible.

If Panama were somehow alerted though, it would be easy enough for my 3 Mavis to carry bombs the 1,800 nmiles north over Mexico to the Galveston, Texas oil refineries/ports. Such would be a minor annoyance to US oil production a la the later Doolittle raid on Tokyo but might serve to shake the confidence of the American public in their 1941 security. Larger than OTL amounts of US military manpower and material would thus be diverted to reinforcing Latin America to the detrement of Pacific islands on the supply route to Australia.

The P-36 fighters are a potent threat to the Mavis if even one squadron intercepts, because the odds will be 3 to 1. At best. Worst case, 9 to 1. The P-36 is slow, but a lot faster than the Mavis. So surprise is absolutely vital. - The questions are, without effective radar could the USAAF defenders of Panama find my 3 widely seperated raiders in the cloudy Panamanian skies and if they somehow could, would the Pan-Am disguises fool the American peacetime fighter pilots ?

I'd say the raid has a good chance of moderate success. Cracking one gate is almost certain if there is no interception before weapons release, two is likely, three is probable. More than three rather unlikely. - Do you base your 50% success rate on the results achieved by the Kido Butai's torpedo pilots at Pearl Harbor ? Prange's book, "At Dawn We Slept" indicates that those pilots acheived 84% torpedo hits when training in Japan with no flak, no smoke and no opposing fighters present. I would suggest that the likely situation that my 3 ATL Mavis would face would be far closer to that training reality with 5 spillwat gate torpedo hits resulting rather than just your 2-3. IMO.

If successful in putting the Panama Canal out of action for six months (although three is more likely), it will be very difficult for the US Atlantic Fleet to reinforce the Pacific Fleet. - This would depend greatly on the number of gates torpedoed and on the amount/timing of rainfall in the Canal's catchment area.

In particular the US carriers Yorktown and Hornet will be delayed in reaching the Pacific. Possibly by around two or three months, as the ships will need to sail right round South America. - AFAIK the Norfolk to San Diego distance via the Panama Canal was 6,000 nautical miles while journeying around the southern tip of South America would add another 8,000 nmiles to that trip. At an average of 16 knots, 8,000 nmiles is an additinal three weeks long.

Perhaps Hitler could have been persuaded to send the full 12 "Operation Drumbeat" type IX U-boats to the Caribbean somewhat earlier to attempt an ambush of any USN warships headed around the Horn as a result ?

And they'll need a brief refit after they arrive, after such a long voyage. - I'd estimate that at only another week.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#7

Post by phylo_roadking » 13 Jan 2009, 01:04

The questions are, without effective radar could the USAAF defenders of Panama find my 3 widely seperated raiders in the cloudy Panamanian skies and if they somehow could, would the Pan-Am disguises fool the American peacetime fighter pilots ?
Well, they're not IN those clouds when over the Canal Zone, they'll be down at attack level...and also the best place to avoid inteception by a very small number of aircraft is in the "look-down" position down on the deck against a rainforest/jungle background :wink: BUT that means a far greater chance of ground aquired early warning.

As for the Panam disguises - it's not as much of a disguise as you may think. Even the regular through-services to South America were flying only every couple of days, their schedules better known to the locals than bus schedules :wink: An aircraft flying OUT of schedule with no radio confirmation would be checked out.
Last edited by phylo_roadking on 13 Jan 2009, 02:15, edited 1 time in total.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#8

Post by Tim Smith » 13 Jan 2009, 01:21

robdab wrote:
I'd say the raid has a good chance of moderate success. Cracking one gate is almost certain if there is no interception before weapons release, two is likely, three is probable. More than three rather unlikely. - Do you base your 50% success rate on the results achieved by the Kido Butai's torpedo pilots at Pearl Harbor ? Prange's book, "At Dawn We Slept" indicates that those pilots acheived 84% torpedo hits when training in Japan with no flak, no smoke and no opposing fighters present. I would suggest that the likely situation that my 3 ATL Mavis would face would be far closer to that training reality with 5 spillwat gate torpedo hits resulting rather than just your 2-3. IMO.
We're not talking about Kido Butai pilots. We're talking about Mavis pilots. And the main job of the Mavis is recon, not torpedo strikes. Mavis pilots will have had far less torpedo practice than Kate pilots. Even if the best Mavis pilots are picked, they are not going to be as good as the Kido Butai Kate pilots.

And this won't be a training flight. And there may be a little flak. And there will be fear of enemy fighters, even if none actually appear. Stress will be high. So expecting an 84% strike rate might be a bit optimistic. Try 66% - four hits out of six.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#9

Post by Simon K » 13 Jan 2009, 01:25

Wouldnt it be better to infilitrate a Japanese Merchant ship into the canal, fitted out with 5 -6 small speedboats, outfitted with one L/L each? Seems a better chance of success and more economic than your extravagant but impressive delivery system :)

I note your views on a Trojan horse. However your arguments against and precautions practiced, would seem insufficient
to stop a determined IJN small boat suicide unit! in fact the whole attack is the ultimate and first "self sacrifice mission"

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#10

Post by ChristopherPerrien » 13 Jan 2009, 02:29

Gee whiz,

The US,by 1941, had in being or building, had a fleet beyond capable of fighting a "two-ocean war". "Worst case scenario planning" on this matter for , I gather , that the enemies would have been Japan and the British Empire, because no-one else,or the rest of world combined, had a fleet capable of contesting US "WORLD" naval supremacy.

As far as how serious closing the Panama canal for 2-3 months, would have done to the US war-fighting capacity , the effect wouyld have been "NIL". The Panama canal as of WWII(39,41 whatever) was only a "bonus", shortening the lenght of voyages for "commercial" craft (i.e more $$$), the effect on the strenght of US Naval strenght was none. We weren't burning coal by WWII, and any or all ,US capital ships could easily go around South America , given two weeks.

Past this, Simply put, for the first few months/years of WWII, America sat half its fleet in the Atlantic, I gather :roll:, defending Britian and its ocean supply lines from one german BB and a few german crusiers. At the same time, America, "fought", Japan with only "one arm". The "strategic/decisive vitality" of closing the Panama canalfor a month or three, pales in light of this.

Chris

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#11

Post by LWD » 13 Jan 2009, 02:36

I'm not sure the canal would be that easy to take by surprise either. Due to German submarine activity in the Carribean at least that side was sending out patrols on a regular basis. The Pacific side may not have been quite as alert but there was a decent amount of AA around the canal in any case from what I recall.

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Simon K
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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#12

Post by Simon K » 13 Jan 2009, 02:42

I agree that the PCs importance may be over emphasised by this point in time.

It isnt approachably as vital a chokepoint that the Suez Canal was to the British Empire.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#13

Post by robdab » 13 Jan 2009, 21:08

Gents,

I hope that a collective answer to several of your postings is ok ...

phylo_roadking, you wrote,

Well, they're not IN those clouds when over the Canal Zone, they'll be down at attack level...and also the best place to avoid inteception by a very small number of aircraft is in the "look-down" position down on the deck against a rainforest/jungle background :wink: BUT that means a far greater chance of ground aquired early warning. - If there was cloud cover that day then my 3 Mavis (Mavises ? Mavii ?) would be hiding in it while using their RDF equipment and the commercial radio station signals to home in on the Gatun Dam area. They would only decend to the lower altitudes below the cloud ceiling, once clear of Panama's higher hills. If bright sunny and clear then yes, they would be flying "down in the weeds".

As for the Panam disguises - it's not as much of a disguise as you may think. Even the regular through-services to South America were flying only every couple of days, their schedules better known to the locals than bus schedules - The 1940 schedule that I have shows daily service on that route and twice daily on the busier portions of it.

An aircraft flying OUT of schedule with no radio confirmation would be checked out. - In peacetime 1941 with the varieties of rainy season weather and the reliability of 1941 aircraft engines, I'd expect any regular civilian schedule to be a hoped for but rarely achieved goal. Espcially in Latin America where attitudes towards strict time schedules have always have always been far more "relaxed" than in North America. The terms "man~ana" and "momentitos" rein.
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Tim Smith, you wrote,

We're not talking about Kido Butai pilots. We're talking about Mavis pilots. And the main job of the Mavis is recon, not torpedo strikes. Mavis pilots will have had far less torpedo practice than Kate pilots. Even if the best Mavis pilots are picked, they are not going to be as good as the Kido Butai Kate pilots. - In the OTL the Kido Butai's pilots trained heavily for the Peral Harbor raids. Both day and night, seven days a week. Why do you feel that my ATL Mavis pilots would not also have been ordered into a similarly intensive training program had the Japanese actually decided to attack the Panama Canal at the same time as Oahu ? The pre-war Japanese were NOT so careless.

And this won't be a training flight. And there may be a little flak. And there will be fear of enemy fighters, even if none actually appear. Stress will be high. So expecting an 84% strike rate might be a bit optimistic. Try 66% - four hits out of six. - Sounds like a reasonable compromise but please see below ...
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Simon K, you proposed,

I note your views on a Trojan horse. However your arguments against and precautions practiced, would seem insufficient to stop a determined IJN small boat suicide unit! In fact the whole attack is the ultimate and first "self sacrifice mission" - I try to write "alternative history" rather than pure fiction. With ship searches by 25 armed and well experienced US troopers, using dogs and followed up by gassing, "insufficient" isn't a word that would fit at 1941 Panama. Such searches were performed long before any vessel even got near a lock entrance, let alone thru any sets of locks and up into Gatun Lake near the spillway gates. Each vessel was anchored under the LARGE calibre guns of a US coastal fortress, and floated over a bottom carpet of American electrically command controlled sea mines which could rip her bottoms out at the mere push of a button should anything appear "wrong". Nah, I don't think that suicide speedboats hidden in a cargo ship are an answer.

AFAIK there were NO officialy planned Japanese suicide missions in 1941. It is true that the 10 minisub crewmen sent in to attack Pearl Harbor had collected hair and nail clippings for return to their families in Japan in case they didn't return but they did have an escape plan in place for pick-up by IJN submarine after the Oahu attacks. Several IJN pilots at Oahu did indeed crash their warplanes into American targets once they had been hit and there was (according to Prange's book ADWS) a torpedo bomber pilot plan to crash their planes into any anti-torpedo netting discovered but such were NOT sanctioned by higher command. Deliberate suicide missions were not official IJN policy in 1941 and so are not allowable in my ATL scenario.

This restriction does not, IMO, rule out the (very real) possibility that a Mavis pilot(s) who missed with his two torpedoes (it was the co-pilot who actually used the ceiling mounted torpedo sight and dropped the "fish") might decide to destroy a spillway gate with his flyingboat, in atonement for his failure(s) and to the Glory of the Emperor. - Banzi !
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ChristopherPerrien, you commented today that,

As far as how serious closing the Panama canal for 2-3 months, would have done to the US war-fighting capacity , the effect wouyld have been "NIL". The Panama canal as of WWII(39,41 whatever) was only a "bonus", shortening the lenght of voyages for "commercial" craft (i.e more $$$), the effect on the strenght of US Naval strenght was none. We weren't burning coal by WWII, and any or all ,US capital ships could easily go around South America , given two weeks. - As best I can estimate from current Panama rainfall records, a repaired Canal would not be back up to full operational status until September 1942. I haven't yet found 1941/2 rainfall records for Panama but I have read of drastic "El Ninio" and "La Ninia" caused rainfall alterations.

Certainly my ATL torpedoing of the Panama Canal would not affect the future US A-bomb research and production schedules nor the comissioning dates of the USN battleships and aircraft carriers already ordered and under construction in 1941. I cannot agree however that there would have been no consequences to the US war effort at all.

Such USN transit around the stormy waters of Cape Horn would certainly result in some warship losses.

Might not German submarines in the South Atlantic or Caribbean take advantage of the more numerous USN targets thus presented to them ?

Many scare fleet oilers, not just tankers, would be required for the underway re-fueling of those 14,000 nmile trips. My readings of the OTL events certainly emphasize that the shortage of American oilers was a very limiting factor for USN missions in the early months of the Pacific War. Certainly a carrier raid on the Japanese Mandate Islands was cancelled when the USS Neches was topredoed and sunk but an IJN submarine and IIRC the attempted Americasn relief of Wake by Admiral Pye was called off due to the USN's lack of refuelling capacity. A knocked out Panama Canal could only make that shortage even more accute.
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LWD, you replied with,

The Pacific side may not have been quite as alert but there was a decent amount of AA around the canal in any case from what I recall. - The Canal is some 50 miles long which results in the dilution of AA assets which at first glance SEEM to be quite numerous but which in reality, were not. My initial posting details the embarressing fact that the few 37mm AA guns present were only equipped with 1 minute's worth of ammunitiion. The bulk of the Ammerican 3" AA defences of late 1941 were deployed to protect the three Canal lock complexes, the coastal fortresses built at either ocean end of the Canal and to defend the closely spaced USAAF airfields. AFAIK the Gatun Dam had no AA guns at all deployed within 6 miles.

And when was the last time that you ordered an apparently civilian airliner to be shot down, in peacetime, for no reason at all, by AA guns that weren't yet deployed within range of that target ?

I believe that your opinion is greatly coloured by your current knowledge of my ATL scenario. Here and now in 2009, you KNOW that my "China Clippers" are torpedo carrying threats to the Gatun Dam's spillway gates. A sleepy peacetime US Army Lt. in charge of a 4 gun 3" AA battery deployed 4 miles to the east of the Gatun locks (the locks, not the dam) would not have any such foreknowledge. From his low to the ground position I would doubt that he could even see a low flying Pan-Am "China Clipper" skimming the surface of Gatun Lake, heading in the direction of the dam. Would he recognize that the "China Clipper" dropping it's two underwing fuel tanks (for a soft landing into that Lake from which they could be recovered and reused) was actually a torpedo attack on the spillway, from about 6 miles away ? What would be threatening about a 4-engined Pan-Am flyingboat coming in for a Lake landing or taking off from same ? In the OTL it was NOT known to the US that the Japanese had even developed a shallow water air dropped torpedo as would be revealed at Pearl Harbor on the same day as my ATL Panama attack. Would his peacetime guns and gunners be sitting ready, uncovered (in the rainy season ?), with ammunition at hand nearby for nearly INSTANT action against an apparently civilian airliner that was doing nothing illegal ?

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Simon K
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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#14

Post by Simon K » 13 Jan 2009, 22:10

That deals with my points.

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Re: Dec.7'41: A Day That Nobody Bombed Panama !

#15

Post by redcoat » 13 Jan 2009, 23:56

Just as a matter of interest, how weak/strong were these lock gates ?

Could they be taken out with a torpedo?

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