What Can Japan Do To Improve The Performance Of Its WW2 Submarine Fleet?

It's quite bewildering that from the huge mass of US fleet carriers and other large combatants flooding the Pacific they haven't hit even one that i can think of from 1943 to 1945 (not counting the already mentioned CVE and CA), despite the good sucess they had against USN CVs and some other large combatants in 1942.
The crux of the matter is aggressiveness, or rather a general lack of it. There was no equivalent of Sam Dealey in the IJN sub service.
 
Can we give them a bit more luck as well? With more subs available and not doing the whole minisub attack fiasco, perhaps the IJN subs can hit and sink Enterprise outside Pearl Harbour in 1941. And maybe sink Saratoga outright either in February or August 1942. And with more subs, maybe some more of them can be send to Midway, maybe forming some additional scouting lines, so maybe at least they'll get to detect Yorktown if nothing else and alert Nagumo?
Could they sink North Carolina as well (that was one incredibly lucky shot, but if the IJN had more subs in the area because they have more to begin with in the first place, who knows?)
The Solomons would have been a great hunting ground for well-led and well-deployed IJN subs. I've long advocated for the IJN to starve the Marines on Guadalcanal by aggressively going after their supply ships with subs.
 
Which 2 US fleet carriers were hit by IJN subs in 1943-44? Or you may perhaps refer to any of Lexington, Independence and Intrepid which were torpedoed by aircraft in that period?

You are correct. Those three were damaged by air attack. A quick check does not turn up specifics of where the attackers were launched from, tho the descriptions of the attacks indicate tactics used by Japanese land based aircraft. The USS Block Island was sunk in 1944, but by a German submarine in the Atlantic.


A partial list thru 1944 of carriers sunk.
  • HMS Courageous Submarine.
  • HMS Ark Royal Submarine
  • HMS Glorious - Surface Ships
  • HMS Audacity - Submarine
  • Shoho - Aircraft
  • USS Lexington - Aircraft
  • USS Yorktown - Submarine
  • IJN Akagi. - Aircraft
  • IJN Hiryu - Aircraft
  • IJN Kaga - Aircraft
  • IJN Soryu - Aircraft
  • HMS Eagle - Submarine
  • IJN Ryūjō - Aircraft
  • UAA Hornet - Aircraft
  • USS Wasp - Submarine
  • IJN Chuyo - Submarine
  • USS Liscombe Bay - Submarine
  • USS Block Island - Submarine
 
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The Solomons would have been a great hunting ground for well-led and well-deployed IJN subs. I've long advocated for the IJN to starve the Marines on Guadalcanal by aggressively going after their supply ships with subs.

Looking at the deployment of the IJN submarines during the Guadalcal battle its difficult to see them employed much more aggressively*. Its also difficult to see how the subs could have done any better at locating the cargo ships than the war ships. Both side submarines were nadicappied by the constricted waters of the region. Everyone was maneuvering around islands, reefs, and highly unpredictable tropical storms. This was not the open waters of the US Coast, the North Atlantic. ect...

(* Here I am differentiating between how the Japanese fleet command used & deployed their submarines, and how the individual sub commanders behaved.)
 
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You are correct. Those three were damaged by air attack. A quick check does not turn up specifics of where the attackers were launched from, tho the descriptions of the attacks indicate tactics used by Japanese land based aircraft. The USS Block Island was sunk in 1944, but by a German submarine in the Atlantic.


A partial list thru 1944 of carriers sunk.
  • HMS Courageous Submarine.
  • HMS Ark Royal Submarine
  • HMS Glorious - Surface Ships
  • HMS Audacity - Submarine
  • Shoho - Aircraft
  • USS Lexington - Aircraft
  • USS Yorktown - Submarine
  • IJN Akagi. - Aircraft
  • IJN Hiryu - Aircraft
  • IJN Kaga - Aircraft
  • IJN Soryu - Aircraft
  • HMS Eagle - Submarine
  • IJN Ryūjō - Aircraft
  • UAA Hornet - Aircraft
  • USS Wasp - Submarine
  • IJN Chuyo - Submarine
  • USS Liscombe Bay - Submarine
  • USS Block Island - Submarine
Good list, though me i would have Yorktown shared equally between aircraft and subs. Crippled by aircraft, finished off by sub.
 
Good list, though me i would have Yorktown shared equally between aircraft and subs. Crippled by aircraft, finished off by sub.
If Akagi, Hiryu, Soryu and Kaga were German then they would have been scuttled.

The USN suffered the same from a lack of aggressiveness due to the pre-war training where commanders were criticised for being discovered rather than being counter attacked and sunk. Coupled with the Mk14 torpedo issues and it was easier to just sack skippers than address the problems.
 
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If Akagi, Hiryu, Soryu and Kaga were German then they would have been scuttled.

The USN attempted to scuttle the Lexington with destroyer torpedos. Those failed & eventually the Japanese found and also torpedoed the burning wreck. Some folks might argue the Lexingtons loss was self inflicted, claiming the damage control decision to vent the rear compartments created the catastrophic fire. I'll let others argue that one.

Good list, though me i would have Yorktown shared equally between aircraft and subs. Crippled by aircraft, finished off by sub.

If we were counting damage rating dry dock then the Yorktown would count as that for aircraft, and a sink for submarines. The fires were out, flooding controlled, and headed back to Oahu at a three knot tow.

Cant believe I left the Hermes off the list. Had it in mind.
 
The USN attempted to scuttle the Lexington with destroyer torpedos. Those failed & eventually the Japanese found and also torpedoed the burning wreck. Some folks might argue the Lexingtons loss was self inflicted, claiming the damage control decision to vent the rear compartments created the catastrophic fire. I'll let others argue that one.
You must refer to Hornet at Santa Cruz? That one was crippled by aircraft, scuttling failed due to the absymal US torpedoes, and later found and torpedoed by IJN. Lexington's scuttling went "Ok" ( if one can use "Ok" for a scuttling). Indeed doomed by avgas vapour explosion.
 
Some folks might argue the Lexingtons loss was self inflicted, claiming the damage control decision to vent the rear compartments created the catastrophic fire. I'll let others argue that one.

Good list, though me i would have Yorktown shared equally between aircraft and subs. Crippled by aircraft, finished off by sub.

Me, I prefer not to split hairs.

I simply take it that every American carrier hit by Japanese aircraft torpedoes suffered from a chain reaction of damage that eventually caused its loss.
 
Me, I prefer not to split hairs.

I simply take it that every American carrier hit by Japanese aircraft torpedoes suffered from a chain reaction of damage that eventually caused its loss.

As referred to in post 38 the Intrepid, Independence, and second Lexington were hit by aircraft torpedos but not sunk. The Saratoga was also hot twice by the larger submarine torpedos and survived both incidents. Luck and good damage control in those cases.

If I had time I'd extend the list to damaged carriers and cause. But on to other things.
 
Compared to the N.Atlantic the IJN subs just can't sink enough to be a grave concern to anything but the most limited and local context. And what does operating in the Indian ocean actually get them in terms of wining the war?

The Imperial Japanese Navy's doctrine of fleet warfare (guerre d'escadre) resulted in its submarines seldom posing a threat to allied merchant convoys and shipping lanes to the degree that the Kriegsmarine's U-boats did as they pursued commerce raiding against Allied and neutral merchant ships. During the war, IJN submarines did sink about 1 million tons (GRT) of merchant shipping (184 ships) in the Pacific; by contrast U.S. Navy submarines sank 5.2 million tons (1,314 ships) in the same period,[5] while U-boats of Nazi Germany's Kriegsmarine, the IJN's Axis partner, sank 14.3 million tons (2,840 ships) in the Atlantic and other oceans.


You could triple the amount the IJN subs sank and it's still just not very much on the scale of WW2 especially when you consider either side's ability to replace losses

Plus as I said the wallie resources in this area just mean they re-adjust resources and go after them, and while those redirected resources have to come from somewhere that's also true for the IJN and the IJN is far more resource strapped than the wallies here, especially as they also have to maintain a huge surface fleet

Plus the Indian ocean is a long way from the Japanese home yards, so they will have to operate from captured territory. This is not problem in itself (the KM operated from France happily enough), but here even those captured bases are also a long way and over water from home yards. It just basically a harder operating context for Japanese Subs..

Just looking at the Indian Ocean it almost twice the size of the North Atlantic,
There is both a tactical and strategic element to submarine warfare. A dozen Axis submarines operating out of Ceylon in mid-1942 would place a huge strain on the Allies. This would be at the tail end of the 2nd Happy Time off the U.S. East Coast, and the return of the U-Boats to the North Atlantic. November 1942 was the highest loss rate to date in the U-Boat War because of the diversion of destroyers and other escorts to support the invasion of North Africa.

The Japanese capture of Ceylon would virtually shut down the Bay of Bengel. This would greatly worsen the factors that led to the famine of 1943 and impede the buildup of Allied forces in Assam slowing long-term add to China. With the large-scale convoys feeding the buildup of ground forces in Egypt that replaced the loses after the Battle of Gazala and made possible the counter offensive at 2nd El Alamein in danger and without extra escorts available to defend them the Allies would have to do a lot of scrambling. It's not enough to just say, "Well the Allies won so they'd win anyway." Some major events are time critical.
 
if they simply told the submarines to hunt supply ships/logistical ships that's the obvious first step
The Pacific is vast, the closest important route is Australia to America, and the Americans outbuilt and outfought the far more numerous German sub threat. It won't do much.
 
There is both a tactical and strategic element to submarine warfare. A dozen Axis submarines operating out of Ceylon in mid-1942 would place a huge strain on the Allies. This would be at the tail end of the 2nd Happy Time off the U.S. East Coast, and the return of the U-Boats to the North Atlantic. November 1942 was the highest loss rate to date in the U-Boat War because of the diversion of destroyers and other escorts to support the invasion of North Africa.

The Japanese capture of Ceylon would virtually shut down the Bay of Bengel. This would greatly worsen the factors that led to the famine of 1943 and impede the buildup of Allied forces in Assam slowing long-term add to China. With the large-scale convoys feeding the buildup of ground forces in Egypt that replaced the loses after the Battle of Gazala and made possible the counter offensive at 2nd El Alamein in danger and without extra escorts available to defend them the Allies would have to do a lot of scrambling. It's not enough to just say, "Well the Allies won so they'd win anyway." Some major events are time critical.
Thing is what will the allies do if they do that? It pretty obvious what happens next if they take Ceylon I agree you can't just argue the allies win anyway, but you also can't say only one side see's a difference when changes happens

Ceylon is far to close to India and and the Indian army and the army in India, Indian air forces etc, Maybe if they launch a surprise attack they can get to it, but their not holding it

Look at what happens OTL there are raids but nothing lasting happens.

I don't like to argue from a position of well if they didn't do they couldn't have done it, by Ceylon is a pretty obvious prize to take and hold in abstract and there was no attempt to

Even if they could take it they're still taking Burma in the first half of 1942, they're not launching an invasion of Ceylon in time to build a sub base (while getting attacked from the mainland) in time to have a dozen subs operating by mid 1942.
 
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November 1942 was the highest loss rate to date in the U-Boat War because of the diversion of destroyers and other escorts to support the invasion of North Africa.
The bulk of tonnage sunk that month was in remote areas where ships sailed independently. The advent of longer ranged u-boats such as the IX D2 gave the Germans better access to the lucrative and relatively safe hunting grounds of the Cape of Good Hope and Indian Ocean etc. In his Hitler's U-Boat War, Blair noted that the high losses of November '42 give the misleading impression of a massacre in the North Atlantic. U-boats did pretty well in the North Atlantic that month, bagging 15 ships from one convoy, but that success was dwarfed by the achievements of the IXs in November.
 
The bulk of tonnage sunk that month was in remote areas where ships sailed independently. The advent of longer ranged u-boats such as the IX D2 gave the Germans better access to the lucrative and relatively safe hunting grounds of the Cape of Good Hope and Indian Ocean etc. In his Hitler's U-Boat War, Blair noted that the high losses of November '42 give the misleading impression of a massacre in the North Atlantic. U-boats did pretty well in the North Atlantic that month, bagging 15 ships from one convoy, but that success was dwarfed by the achievements of the IXs in November.
Yes the U-boats were operating in the Indian ocean, so I'm really not sure what another dozen Japanese subs will add here. I asked easier (linking the sub attacks in the Indian ocean at that point) just how much were the Japanese subs were responsible for, IMO if you look the German u-boats are more than pulling their weight.
 
Yes the U-boats were operating in the Indian ocean, so I'm really not sure what another dozen Japanese subs will add here. I asked easier (linking the sub attacks in the Indian ocean at that point) just how much were the Japanese subs were responsible for, IMO if you look the German u-boats are more than pulling their weight.
Yes of course. A key problem was that IJN subs (notably big ones like New Junsens) weren't designed for a war on commerce. Unlike type VII u-boats, and even most IXs, I-boats were too big to approach undetected on the surface at night. Aware of this problem, the Germans sent Japan a couple of IXs to copy, but they didn't get through.
 
Thing is what will the allies do if they do that? It pretty obvious what happens next if they take Ceylon I agree you can't just argue the allies win anyway, but you also can't say only one side see's a difference when changes happens

Ceylon is far to close to India and and the Indian army and the army in India, Indian air forces etc, Maybe if they launch a surprise attack they can get to it, but their not holding it

Look at what happens OTL there are raids but nothing lasting happens.

I don't like to argue from a position of well if they didn't do they couldn't have done it, by Ceylon is a pretty obvious prize to take and hold in abstract and there was no attempt to

Even if they could take it they're still taking Burma in the first half of 1942, they're not launching an invasion of Ceylon in time to build a sub base (while getting attacked from the mainland) in time to have a dozen subs operating by mid 1942.
Thank you for your reply. The reason nothing long term happened was because the IJA didn't want to provide the troops for an invasion when Ceylon was vulnerable, so the IJN settled for a raid and never came back. If the IJA provided 2 divisions, they would've taken the Island in April 1942. As for the Indian reaction not, much could happen for at least a year. They had no bases in southern India to stage an air siege of Ceylon, and there are no air forces to send there because their busy elsewhere trying to hold the line in Burma and Egypt. If they can't use the Bay of Bengal, they can't ship anything in.

As for building a sub, base on Ceylon the RN already had one and most of the port facilities would be captured before serious destruction would be possible. In real life blowing up a port is no easy task and needs a lot of time and preparation. In fact, there were several large ports on Ceylon that could be used for naval purposes. If the ATL decision is made to invade Ceylon and conduct major operation in the Indian Ocean the Midway Operation is at least on hold, but the Japanese could continue to advance in the Solomons. Nothing the Japanese could do in 1942 could hurt the Allies more than a long-term surge into the Indian Ocean.

In the event of the Japanese making such a move the British planned to move the bulk of their naval forces into the Indian Ocean. This would include all of their modern carriers, and most of their battleships. In a daytime carrier battle the RN would probably lose badly, so such an action would need to be avoided. They were fortunate that they didn't lose the modern carriers Formidable & Indomitable during the raid on Ceylon. Nagumo made a serious mistake in not putting out adequate search patrols. As it was his patrols came within 50 miles of finding Force A, and at one point both fleets were about 100 miles apart. A small strike force actually attacked the Japanese but scored no significant damage, and most of the aircraft were lost. Finding Force A would probably be its death sentence.

Once the Japanese have ships, subs, and aircraft on Ceylon the strategic danger for the Allies escalates dramatically. It would seriously change Allied global strategy for 1942 and effect major events for the rest of the war.
 
Yes the U-boats were operating in the Indian ocean, so I'm really not sure what another dozen Japanese subs will add here. I asked easier (linking the sub attacks in the Indian ocean at that point) just how much were the Japanese subs were responsible for, IMO if you look the German u-boats are more than pulling their weight.
The Indian Ocean was the vulnerable area in 1942. What the Germans call the Zeitpunkt should have been pushed harder on. The German Type IX Boats were doing very well but would've done better with an operational base in the region. Adding a half a dozen Japanese subs and the pressure on the Allies becomes much greater. In 1942 the Allies are sending vital convoys to Egypt, (To stop Rommel) Iran, (For Russia) and Assam, (Which effects China).
 
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