Feasibility of massed submarine attacks on task forces in WW2?

It is noteworthy, given the speed of fleet carriers and the slow speed of submarines that more aircraft carriers were sunk by sub-launched torpedoes than other causes.

Of the eleven USN carriers lost in combat, four were lost to submarines.

USS Yorktown (CV-5)
USS Wasp (CV-7) - Later Scuttled By USN
USS Liscomb Bay (CVE-56)
USS Block Island (CVE-21)

Of eight RN carriers lost in combat, five were lost to submarines.

HMS Courageous
HMS Eagle
HMS Ark Royal
HMS Audacity
HMS Avenger

In total, the Wallies lost nineteen aircraft carriers in combat, nine of which to submarine launched torpedoes. Of the other ten carrier losses; HMS Dasher exploded allegedly due to poor fuel vapor handling, HMS Glorious and USS Gambier Bay were lost to surface gunfire, while the other seven were lost to aerial attack, sometimes forcing friendly-fire scuttling.

This obviously supports the idea of having your submarines in the right place at the right time, rather than having them sprint to catch the enemy CBG.

Thanks for that, it also suggests the Japanese doctrine of using the subs vs capitol ships was not entirely wrong. Their subs did as well or better than the IJN carriers in putting US carriers out of action.
 
Thanks for that, it also suggests the Japanese doctrine of using the subs vs capitol ships was not entirely wrong. Their subs did as well or better than the IJN carriers in putting US carriers out of action.
Of note, of the twenty IJN carriers lost, I count eight lost to submarines.

https://en.wikipedia.org/wiki/List_of_sunken_aircraft_carriers#Japan

So, who lost the most carriers to submarines?

Britain - 8 losses, 5 to submarines (63%)
USA - 11 losses, 4 to submarines (36%)
Japan - 20 losses, 8 to submarines (40%)

The moral of the story for safe carrier ops is not to neglect your underwater protection and ASW.
 
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The most effective use of the Japanese submarine force would have been an anti-shipping campaign.

Sure in principle that would've been best. One problem, though, is that IJN subs weren't particularly well suited for anti-shipping operations. They were too big, which meant too easy to spot, hence less able to make night surface attacks (IJN sub successes against US warships resulted from submerged attacks). The Germans wanted the Japanese to build smaller boats based on their type IXs and sent a couple to Japan.



They could have forced the US to develop a serious convoy system for the West Coast like the East Coast, between California and Hawaii, and on the routes to Australia. This would have slowed things down for the US, cost the US supplies and ships that would go under, and divert US naval resources that OTL were used elsewhere as well as potentially affecting naval construction program (more escorts needed).

In their epilogue the authors of the aforementioned tome had the same recommendation. In the first 13 months of the war, they wrote, the IJN should've positioned all ocean going and fleet type subs off the US Pacific coast and Hawaii. Besides what you mention, they might've bagged some of the old BBs on their way back to the states for repairs. The authors say the subs should also have attacked the Panama canal, scaring the US into building elaborate defenses there at the expense of Pacific operations.
IMO, though, the IJN subs should've focused on the Indian Ocean, where they did best OTL. Actual operations near the US Pacific coast in '42 achieved little. In the Indian Ocean, IJN subs continued to bag a fair amount of shipping down to early '44. They could've sunk a heck of a lot more if the subs slaughtered in the Marianas--at least 20 IIRC--reinforced those at Penang etc.
 
Sure in principle that would've been best. One problem, though, is that IJN subs weren't particularly well suited for anti-shipping operations. They were too big, which meant too easy to spot, hence less able to make night surface attacks (IJN sub successes against US warships resulted from submerged attacks). The Germans wanted the Japanese to build smaller boats based on their type IXs and sent a couple to Japan.
They should have partnered up earlier on. Japan sells some fast CVLs to Germany, Germany sells some agile subs (with Pacific mods for range and living) to Japan. Italians can sell tanks to Japan, lol.
 

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Why would Germany buy light carriers? If they REALLY wanted a carrier they could have finished their own.

They should have partnered up earlier on. Japan sells some fast CVLs to Germany, Germany sells some agile subs (with Pacific mods for range and living) to Japan. Italians can sell tanks to Japan, lol.
 
Why would Germany buy light carriers? If they REALLY wanted a carrier they could have finished their own.

True, but Graf Zeppelin was a mess. A more functional carrier would have helped, as well as Japan selling them some modern carrier-capable aircraft...
 
Why would Germany buy light carriers? If they REALLY wanted a carrier they could have finished their own.
They would have finished their own if they'd had the time and resources. I suggest fast CVLs since they'll be cheaper and faster for Japan to build and for Germany to buy. Imagine the KM Norway campaign if they had two or three CVLs equal to the later converted Chitose-class aircraft carriers (15,000 tons, 29 knots, 30 aircraft), especially if they were delivered to Germany (with trained crews and aircraft) without warning in 1938-39, meaning the RN will be hard pressed to modify its own carrier programs to react.

However this is entering the realm of threadjacking, so I will say no more that leads us OT.
 
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I did actually mean battleships. My idea is that submarines swarm the opposing fleet, trying their utmost to sow chaos by pulling destroyers out of optimal positions, and firing many torpedoes in the direction of the most appealing targets. Is there a better way I'm missing, for them to attack warships?

Well being in the receiving area where your own fleet is lobbing shells generally in the area you (as the sub commander are) doesn't sound too appealing to me!
 
Other than getting lucky no.

It's possible to get lucky and call in a strike. IE submarine gets lucky on a carrier flight operations is not workable for four hours and you send in your strike package but it relies on luck.

In reality though the best you can do is get a trip wire open and make them go through it.

WW2 submarines in general are approximately 2/3-3/4 fleet speed when not submerged and 1/4-1/3 fleet speed when submerged so they don't get to choose to battle fleet units.

The situations are similar why didn't they get help from Germany?
 
German ships were optimized for the Atlantic - temperatures, distances/range etc. Japanese subs were optimized for Pacific ops. The Japanese would have had to stop production of their subs and build copies of U-boats, retooling etc to do this. Before the war the Germans did not have any front line boats to spare, and after PH transferring any, and Germany still needs all they have, is impractical. As far as Japan giving Germany CVLs they don't have any to give away. Assuming the Germans can build or modify existing aircraft for carrier service, realistically speaking it would take at least 12 and up to 24 months to get the ship combat ready, and that is assuming the pilots have at least good at practice carrier landings on a land base on day one and are ready to qualify as soon as the ship arrives and can go to sea. So you are talking about delivery no later than 1936/37 and aircraft design and pilot training before that.
 
German ships were optimized for the Atlantic - temperatures, distances/range etc. Japanese subs were optimized for Pacific ops. The Japanese would have had to stop production of their subs and build copies of U-boats, retooling etc to do this.

Well, the Japanese weren't only building big New Junsens. They were building subs of all kinds and sizes; one author called their building program "anarchic."

Before the war the Germans did not have any front line boats to spare, and after PH transferring any, and Germany still needs all they have, is impractical.

Transferring IXs to Penang, Surabaya etc was feasible and provided they operated in the Indian Ocean they could still serve German as well as japanese war aims e.g. interdicting allied supplies for the USSR via the Cape of Good Hope and Persian Gulf. The main advantage of operating out of Penang was the lesser threat from allied ASW assets. Of course had the Germans begun shifting all IXs to Japanese bases beginning in the spring of '43 the allies would've sent more planes and destroyers to Australia and India. If the Germans had a head start, though, they could've bagged a lot of ships in 1943-early '44.
 
Type IXs operating out of Penang (as OTL) but in much larger numbers and sooner has several issues. The more German U-boats you have, the more you need spare parts, various sorts of armaments not compatible with the Japanese, and a robust shore establishment. Once you begin to get a significant number of Kriegsmarine boats operating out of Penang you need mechanics, medical personnel, clerks to support the operating U-boats. The Japanese simply do not have extra shore establishment and logistic train to support what is, in essence, a German naval base in Penang. There will also be the issue at some point of adequate decent fuel for the U-boats, at some point the Japanese had to operate warships on basically unrefined fuel because while they had crude, refinery capacity was limited.

Sending U-boats to Penang means that you risk losing some on the way, and I expect the rules for the trip would be to avoid any contact unless a particularly juicy target shows up in front of you. This takes each U-boat out of the war for an extended period before it arrives in Penang and some permanently. To interdict shipping from the Cape of Good Hope to the Persian Gulf means operating well away from the base in Penang, and you have Allied air support/coverage available pretty much all the way. While cutting some of the supplies to Russia does help Germany some, would sinking the same tonnage or even more in the Atlantic or the Murmansk route be better? Certainly sinking supplies to Russia does zero for Japan. If the U-boats attack shipping in the Eastern Indian Ocean, traffic to/from Australia, traffic to/from Ceylon this is "easier" then attacking traffic enroute to the Gulf from the Cape of Good Hope this effort does little to aid German interests. Any minimal effect this has on Australia-Middle East traffic is not much and won't affect the Axis being evicted from North Africa.

The reality is that in WWII cooperation between the "western" Axis (Germany et al) and Japan was pretty minimal. They basically fought two separate wars, and prior to 1941 contingency planning, technical exchanges and so forth was minimal to nonexistent.
 
Type IXs operating out of Penang (as OTL) but in much larger numbers and sooner has several issues. The more German U-boats you have, the more you need spare parts, various sorts of armaments not compatible with the Japanese, and a robust shore establishment. Once you begin to get a significant number of Kriegsmarine boats operating out of Penang you need mechanics, medical personnel, clerks to support the operating U-boats. The Japanese simply do not have extra shore establishment and logistic train to support what is, in essence, a German naval base in Penang. There will also be the issue at some point of adequate decent fuel for the U-boats, at some point the Japanese had to operate warships on basically unrefined fuel because while they had crude, refinery capacity was limited.

The Germans planned to use their Italian subs as cargo carriers to the Far East. The problem was, by the time this was done--largely in response to the needs mentioned above--the allies had more means to thwart missions, so few got through. Things might've been better had the decision been made sooner due to more boats heading to Penang, Surabaya etc.


Sending U-boats to Penang means that you risk losing some on the way,

The main threat was the Ascension Island base and hunter killer groups but I don't think either became a serious problem, in the South Atlantic, prior to about the fall of '43.


and I expect the rules for the trip would be to avoid any contact unless a particularly juicy target shows up in front of you.

Sinking unescorted vessels wasn't a problem.


To interdict shipping from the Cape of Good Hope to the Persian Gulf means operating well away from the base in Penang, and you have Allied air support/coverage available pretty much all the way.

The distance wasn't a problem for IXs especially IXd2s and while Allied ASW assets became stronger, the area was a heck of a lot less dangerous than the North Atlantic.

While cutting some of the supplies to Russia does help Germany some, would sinking the same tonnage or even more in the Atlantic or the Murmansk route be better?

Indian Ocean operations would almost certainly be less costly and just as good. IIRC more supplies reached the USSR via the Persian gulf than murmansk.


Certainly sinking supplies to Russia does zero for Japan. If the U-boats attack shipping in the Eastern Indian Ocean, traffic to/from Australia, traffic to/from Ceylon this is "easier" then attacking traffic enroute to the Gulf from the Cape of Good Hope this effort does little to aid German interests. Any minimal effect this has on Australia-Middle East traffic is not much and won't affect the Axis being evicted from North Africa.


Maybe so, but at least this way the u-boats could still accomplish something. By 1944 they were sinking very little in the Atlantic anymore, while getting massacred.
 
The Allies were reading 10% of JN25b encoded messages at start of war and 70% by May 1942.
That's the high-grade cypher. AIUI, they were reading the movement cypher, which would reveal which units moved where & when, from the very start.
 
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