Defeating Invasion Fleets

Discussions on alternate history, including events up to 20 years before today. Hosted by Terry Duncan.
glenn239
Member
Posts: 5845
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Defeating Invasion Fleets

Post by glenn239 » 21 Feb 2023 18:02

thaddeus_c wrote:
21 Feb 2023 05:34

was posing that development of the smaller subs against the resupply of Allied forces, not stopping the landings (the same may be true of both, but I was alluding to the former.)
Makes sense.

The other weapon system to consider would be pressure mines which, if deployed in adequate numbers and in conjunction with strong landward defenses, might have proven a major challenge to even the largest of Allied invasions.

User avatar
T. A. Gardner
Member
Posts: 3513
Joined: 02 Feb 2006 00:23
Location: Arizona

Re: Defeating Invasion Fleets

Post by T. A. Gardner » 22 Feb 2023 03:21

If you have the manufacturing capacity, and the raw materials for it, you could make command detonated mines. These are frequently found as part of coast defense systems protecting harbors and other such choke points.

Carl Schwamberger
Host - Allied sections
Posts: 10028
Joined: 02 Sep 2006 20:31
Location: USA

Re: Defeating Invasion Fleets

Post by Carl Schwamberger » 22 Feb 2023 15:34

Logical extension of the command detonated mine would be shore based torpedos. ie: sinking the Blucher.

The Japanese with this high quality torpedos and excellent tactics achieved hits rates of 7% at the low end and 10-12 % at the upper end from their attacks from surface ships. So, 50 torpedos launched vs a off shore surface fleet may get you 5 hits on the enemy fleet. That is assuming the pre invasion bombardments do not neutralize the torpedo launch site. Perhaps acoustic homing torpedos would get a higher hit rate. USN & IJN aircraft using dive bombers and torpedos achieved a much higher hit rate 15% at the low end to 25%. Higher in a few extreme cases. The down side you seldom had more than fifty bomber sorties in 24 hours until 1944 or later.


The Battle of the Bismarck Sea, or Operation 81 in Japanese terms, was strictly speaking not a amphib operation as the OP specified. But, if we are following the 21st Century USN/Marines doctrinal view of Littoral Warfare then the defeat of Op 81 is worth a look. In short the Japanese embarked some 6000 soldiers and supplies from the 51st Inf Div for transport from Simpson Harbor to Lae on New Guinea. The US 5th Air Force and Australian RAF made a combined air attack of 50+ aircraft, mostly strafing & using skip bombing techniques. I don't know how may bombs were dropped, but all eight transports & half the escorts were sunk. So, 6-7 sorties per ship sunk, which is fairly good for large scale attacks. I'd have to review the result of Op PEDESTAL but seem to remember the Axis air strikes were sinking about one Allied ship per 40 sorties. At Midway it was 50+ dive and torpedo bomber sorties per carrier sunk. For Ops HUSKY, AVALANCHE & SHINGLE I've not a clue how many sorties were flown vs the invasion fleets. Technically the German launched 310 sorties at the 6th June invasion. But, not all those were aimed at the fleet or attacked it.

User avatar
wm
Member
Posts: 8744
Joined: 29 Dec 2006 20:11
Location: Poland

Re: Defeating Invasion Fleets

Post by wm » 22 Feb 2023 17:40

The problem is because the Germans don't know where the invasion fleet is going to land, they can't concentrate against it.
If, by a miracle, the Germans concentrate sufficient forces; the invasion fleet won't come.

So the only solution was Wunderwaffe.
Even more, the wonder weapon could only be used successfully only once - because the next time, the Allies would adapt and deploy countermeasures (as it happened to Fritz X, where serious resources to defeat it were deployed very fast).

It follows then the wonder weapon should have been used against Neptune because only its defeat would radically change the course of the war - not against the earlier operations.

User avatar
T. A. Gardner
Member
Posts: 3513
Joined: 02 Feb 2006 00:23
Location: Arizona

Re: Defeating Invasion Fleets

Post by T. A. Gardner » 22 Feb 2023 17:58

Carl Schwamberger wrote:
22 Feb 2023 15:34
Logical extension of the command detonated mine would be shore based torpedos. ie: sinking the Blucher.

The Japanese with this high quality torpedos and excellent tactics achieved hits rates of 7% at the low end and 10-12 % at the upper end from their attacks from surface ships. So, 50 torpedos launched vs a off shore surface fleet may get you 5 hits on the enemy fleet. That is assuming the pre invasion bombardments do not neutralize the torpedo launch site. Perhaps acoustic homing torpedos would get a higher hit rate. USN & IJN aircraft using dive bombers and torpedos achieved a much higher hit rate 15% at the low end to 25%. Higher in a few extreme cases. The down side you seldom had more than fifty bomber sorties in 24 hours until 1944 or later.


The Battle of the Bismarck Sea, or Operation 81 in Japanese terms, was strictly speaking not a amphib operation as the OP specified. But, if we are following the 21st Century USN/Marines doctrinal view of Littoral Warfare then the defeat of Op 81 is worth a look. In short the Japanese embarked some 6000 soldiers and supplies from the 51st Inf Div for transport from Simpson Harbor to Lae on New Guinea. The US 5th Air Force and Australian RAF made a combined air attack of 50+ aircraft, mostly strafing & using skip bombing techniques. I don't know how may bombs were dropped, but all eight transports & half the escorts were sunk. So, 6-7 sorties per ship sunk, which is fairly good for large scale attacks. I'd have to review the result of Op PEDESTAL but seem to remember the Axis air strikes were sinking about one Allied ship per 40 sorties. At Midway it was 50+ dive and torpedo bomber sorties per carrier sunk. For Ops HUSKY, AVALANCHE & SHINGLE I've not a clue how many sorties were flown vs the invasion fleets. Technically the German launched 310 sorties at the 6th June invasion. But, not all those were aimed at the fleet or attacked it.
The US would have done better in terms of hits as by 1943 pilots were getting far better training in how to attack and sink ships. The USAAF was training crews in California on the "Muroc Maru" as it became known. This was a full scale mock up of a Japanese cruiser for bomber crews to practice on.

Image

Carl Schwamberger
Host - Allied sections
Posts: 10028
Joined: 02 Sep 2006 20:31
Location: USA

Re: Defeating Invasion Fleets

Post by Carl Schwamberger » 22 Feb 2023 18:43

T. A. Gardner wrote:
22 Feb 2023 17:58
... The US would have done better in terms of hits as by 1943 pilots were getting far better training in how to attack and sink ships. The USAAF was training crews in California on the "Muroc Maru" as it became known. This was a full scale mock up of a Japanese cruiser for bomber crews to practice on.

Image
A lot of poorly tested or developed prewar doctrine had to be abandoned. Or shelved doctrines revived. Blame Congress which slashed War & navy Department budgets every two year budget cycle from 1920 through 1936. 1938 budget bill (for 1939-40) was the first budget significantly increasing military expenditure in 18 years. The Army and Navy had to reduce or shelve successive development & training programs each budget cycle. Kennys attention to low level attack techniques reflected his training in 'Strike Aviation' in the 1920s. But that training and aircraft development virtually ceased from the mid 1930s as the Army Air Corps concentrated its thin dribble of R & D on the YF17 project and long range operations. Kennys experiments & training for low level & skip bombing attack techniques was picking up where the AAC left off a decade earlier. Through 1938 the Army had exactly one viable armored vehicle project, the embryonic M2 medium tank. The Navy sacrificed other R & D project in 1938 to continue its radio range & direction finding experiments. In 1939 there was a allocation of all of $1,500 of Navy funds for a study of using radioactives for propulsion power.

In the early 1920s Army CoS Peyton Marsh and later Pershing proposed robust R & D programs & industrial reserve for national defense. Congress would have none of it it and for near two decades funding only token programs & directed dismantling others. In 1922 the Army still possessed eight motorized artillery regiments. The next budget cycle mandated eliminating six of those and reducing the other two to a 40% strength training cadre. Effective training was reduced to hand fulls of top officers attending the War Colleges and Staff & Command schools. Field training became Regiment, Brigade, Divison, and Corps HQ exercising a half dozen token battalions.

The relative successes of Kennys 5th AF vs the japanese Op 81 convoy had to do with five plus months of previous testing and training by Kennys favorite Major Benn, with the 63rd Squadron. A hulk on a Australian reef, the former SS Pruth, was attacked over and over in dozens of trials, the effects studied, and then attacked again in dozens more training flights of the 5 AF bomber division.

Peter89
Member
Posts: 2369
Joined: 28 Aug 2018 05:52
Location: Europe

Re: Defeating Invasion Fleets

Post by Peter89 » 22 Feb 2023 22:11

The fundamental problem with air power is that it is very expensive and complicated. Naval power is less complex but also very expensive. If someone wants to fight off a major invasion, he has to rely on ground forces. A major invasion would not materialize without air and naval superiority anyway.

Also torpedoes are very expensive. It is far more sensible to use mines and artillery.
"Everything remained theory and hypothesis. On paper, in his plans, in his head, he juggled with Geschwaders and Divisions, while in reality there were really only makeshift squadrons at his disposal."

User avatar
wm
Member
Posts: 8744
Joined: 29 Dec 2006 20:11
Location: Poland

Re: Defeating Invasion Fleets

Post by wm » 22 Feb 2023 22:52

Exactly but I'm thinking about Hitler's idea of a fast, impossible-to-intercept jet bomber. The Luftwaffe hated it and did nothing, but technically such a bomber was possible in 1944, so we don't need too much magic dust here.

Flying high jet bombers armed with a (slightly improved and kept secret) Fritz-X probably would be effective, and there would be no need for hundreds of them, just a few dozens (assuming it's true they would be really very hard to intercept.)

Peter89
Member
Posts: 2369
Joined: 28 Aug 2018 05:52
Location: Europe

Re: Defeating Invasion Fleets

Post by Peter89 » 23 Feb 2023 07:10

wm wrote:
22 Feb 2023 22:52
Exactly but I'm thinking about Hitler's idea of a fast, impossible-to-intercept jet bomber. The Luftwaffe hated it and did nothing, but technically such a bomber was possible in 1944, so we don't need too much magic dust here.

Flying high jet bombers armed with a (slightly improved and kept secret) Fritz-X probably would be effective, and there would be no need for hundreds of them, just a few dozens (assuming it's true they would be really very hard to intercept.)
For that we need airstrips, crews, spare parts, fuel, tons of highly complex equipment and of course a steady inflow of all.

It is also questionable how effective Fritz-X would be against fast, small, nimble targets from an extremely fast plane.

Any wireless system is easier to jam than protected from jamming.

In my opinion, the Germans best chance was to deliver an explosion to the landing troops at the time of their utmost vulnerability, during the landing proper. This could come from wire controlled mines or shells.
"Everything remained theory and hypothesis. On paper, in his plans, in his head, he juggled with Geschwaders and Divisions, while in reality there were really only makeshift squadrons at his disposal."

User avatar
wm
Member
Posts: 8744
Joined: 29 Dec 2006 20:11
Location: Poland

Re: Defeating Invasion Fleets

Post by wm » 23 Feb 2023 14:17

The jet bomber was a generic weapon - badly needed everywhere, useful, and nice to have - it wasn't a nine-day wonder just to defeat the fleet.
So it wasn't a bad idea to have them anyway.

The transport ships, cruisers, and battleships weren't that nimble. And without a majority of them, the rest might as well go home.

As the plane has to approach the target head-on, its speed isn't such a problem - at 200 m/s, it's 25 seconds to the target (from the maximum range of Fritz-X) - plenty of time to correctly guide the missile.

Yes, the Fritz-X was easy to jam, but you had to know how to do it, and weeks were needed just to find out how.

OpanaPointer
Financial supporter
Posts: 5593
Joined: 16 May 2010 14:12
Location: United States of America

Re: Defeating Invasion Fleets

Post by OpanaPointer » 23 Feb 2023 14:23

Where's Archimedes when you need him? https://en.wikipedia.org/wiki/Archimedes
Come visit our sites:
hyperwarHyperwar
World War II Resources

Bellum se ipsum alet, mostly Doritos.

Peter89
Member
Posts: 2369
Joined: 28 Aug 2018 05:52
Location: Europe

Re: Defeating Invasion Fleets

Post by Peter89 » 23 Feb 2023 16:26

wm wrote:
22 Feb 2023 22:52
Exactly but I'm thinking about Hitler's idea of a fast, impossible-to-intercept jet bomber. The Luftwaffe hated it and did nothing, but technically such a bomber was possible in 1944, so we don't need too much magic dust here.

Flying high jet bombers armed with a (slightly improved and kept secret) Fritz-X probably would be effective, and there would be no need for hundreds of them, just a few dozens (assuming it's true they would be really very hard to intercept.)
Yes, the jet bombers were nice to have, although Germany was nowhere near to mass produce and employ them in their time.

The Fritz-X was indeed good against large warships like battleships. But against landing crafts? Not really. Of course if we are talking about a blue water invasion fleet, one that comes from open ocean, then Fritz-X might be relevant. In the Channel, not so much.
"Everything remained theory and hypothesis. On paper, in his plans, in his head, he juggled with Geschwaders and Divisions, while in reality there were really only makeshift squadrons at his disposal."

glenn239
Member
Posts: 5845
Joined: 29 Apr 2005 01:20
Location: Ontario, Canada

Re: Defeating Invasion Fleets

Post by glenn239 » 23 Feb 2023 18:11

Peter89 wrote:
23 Feb 2023 07:10
In my opinion, the Germans best chance was to deliver an explosion to the landing troops at the time of their utmost vulnerability, during the landing proper. This could come from wire controlled mines or shells.
Remote detonated minefields would be a serious threat in theory, but I doubt in practice - Allied sapper teams would cut the wires on the beach routes before the invasion.

Carl Schwamberger
Host - Allied sections
Posts: 10028
Joined: 02 Sep 2006 20:31
Location: USA

Re: Defeating Invasion Fleets

Post by Carl Schwamberger » 23 Feb 2023 18:24

Running back down the rough list I have two observations emerge. First: is that small landing forces seem particularly prone to be aborted or defeated, either from the covering force being damaged, or less often the transport group damaged. Examples of the defeat of the covering force would be Wake island, Midway, or Milne Bay (the Coral Sea battle). In these cases its more often the key commanders deciding the covering force cant do its mission, than any actual defeat. Broken morale as it were? Or misplaced judgement?

Second: Largish invasion forces are much more difficult to abort or defeat via attacking the transport of covering fleet. Crete is one of the very few examples of a landing force larger than a commando group tactically defeated at sea. Other examples like Balikipan, Java, Trondheim, Narvik, the timing is off. With the landing force ensconced ashore & not immediately affected by the loss of part of all the fleet. In the case of the Kerch Peninsula operation the second hand sources attribute at least part of the defeat of the ground forces ashore to destruction of a portion of the transport and combat fleet. However I'd want to find details on numbers of ships sunk and proportion of supplies lost.

If examined in the context of littoral warfare rather than specific beach assault or landing forces the picture becomes a little broader. The PoV is more operational than tactical, with a longer time span. In that context the Narvik operation becomes a near defeat with the German force ready to pack it in and flee to neutral Sweden. Examples like the Guadalcanal battle for both sides become relevant, with the US naval force able to sustain the ground force, and the Japanese defeated in this respect. Ditto for New Guinea. At the extreme end might be the Axis lodgment in Tunisia, which collapsed when the cargo fleet could no longer sustain the losses on the run to Bizerte/Tunis. Again I don't have details on ships and cargo lost.

Carl Schwamberger
Host - Allied sections
Posts: 10028
Joined: 02 Sep 2006 20:31
Location: USA

Re: Defeating Invasion Fleets

Post by Carl Schwamberger » 23 Feb 2023 18:26

OpanaPointer wrote:
23 Feb 2023 14:23
Where's Archimedes when you need him? https://en.wikipedia.org/wiki/Archimedes
Im trying to visualize Germanic versions of Archimedes engines sinking LCI & LST off GOLD or UTAH beaches.

Return to “What if”