Better Japanese Submarine tactics

At the beginning of the war Japan had a decent fleet of submarines, and excellent torpedoes. Yet, they accomplished very little during the war due to operational doctrine that saw them as scouts and as weapons against warships. Eventually many of their larger/long range submarines ended up being impromptu cargo & troop carriers to many outlying garrisons as US subs decimated the Japanese merchant marine.

Let us assume (major hand wave here) that in return for some German aviators training in Japan for carrier ops on the planned German carriers, some Japanese submariners go to Germany to discuss submarine tactics with the U-boat veterans of WW1 and the new officers of the Kriegsmarine U-Boot Flott. All of this takes place BEFORE the outbreak of war, and the returning officers manage to convince the powers that be in the IJN that an anti-merchant campaign should be tried.

So, after Pearl Harbor you have a substantial number of Japanese submarines in place along the west coast of the US, the US-Hawaii route, the western approaches to the Panama Canal. Later subs will be dispatched along the Hawaii-Samoa-Australia axis. I predict the Japanese subs on the west coast will have a happy time even better than the Germans on the east coast - as they commence operations the afternoon of Dec 7 whereas the US had at least some time to get ready before the German U-boats arrived. After the first 4-6 months things get tougher for the Japanese, but ASW escorts and ASW air patrols needed for the Pacific over & above what went there OTL will either mean shifts in ship building and a/c building priorities, shifts in what we do have (more escorts go to the Pacific and 4 engine a/c that might have gone to England to bomb Europe are used for ASW patrols - the Navy used B-24s, why not B-17's esp along CA coast & off Panama).

IMHO this may slow things down a little in the Pacific, but diversion of effort from Europe will be necessary. Love to hear comments.
 
[...] the returning officers manage to convince the powers that be in the IJN that an anti-merchant campaign should be tried.

This'd be a very hard sell, as merchant shipping would not be seen as honorable targets for a warrior of bushido. Not to say that the prize wouldn't be worth the effort, only that it'd be difficult to convince the PTB to consider the idea.
 
I predict the Japanese subs on the west coast will have a happy time...


Sloreck,

This is the third time I've linked this page to a thread here in the last 24 hours.

You're looking at much bigger problem than a couple of KM exchange officers can fix. Let me provide this quote for those who don't want to follow the link:

In the face of such disadvantages, morale declined within the Japanese submarine force. This is reflected in a post-war report prepared by the US and British Navies which states, "It was frankly impossible to believe that submarines could spend weeks on the US west coast 'without contacts,' or spend more than 40 days running among the Solomons during the Guadalcanal campaign 'without seeing any targets.' Even the Japanese commanding officers could not disguise their embarrassment when recounting these tales. Further enlightenment is found in the extremely large number of times the target was 'too far away to attack.'"

The trouble wasn't with the IJN's operational doctrine for submarines. The trouble was with the men in those submarines. You don't spend weeks off the West Coast of the US with orders to sink merchantmen and report that you had no contacts. You don't spend an entire patrol in the Solomons and report you didn't see anything either.

All of the war's major navies had troubles with the commanding officers in their submarines. Some men simply couldn't do it, despite all the training they had, and some men could do it, but only for a few patrols. The RN, KM, and USN all quickly learned that you had to ruthlessly replace officers aboard submarines at the first signs of inability, the same navies also learned how to spot the kinds of men who may be good submariner officers, and the IJN somehow never managed to learn those two lessons.

Assuming Japan manages to produce a credible submarine threat along the transport routes you mentioned, the US would simply take the same precautions it was already taking in the Atlantic. The submarine threat posed by the IJN is not going to be anything remotely similar to that posed by Germany either as Japan will have so fewer boats - only 174 in the entire war - attempting to find and sink vessels in a much larger ocean.


Bill
 
I agree with the posters who have made the point that getting the Japanese to change doctrine, and to get appropriately aggressive sub commanders requires major hand waving or butterflies, hopefully not at the ASB level. However let's just assume they do this (this is alt-hist), and I'm not asking for them to produce huge numbers of submarines as they simply don't have the capacity to do more than a modest increase in numbers, and only if they start before the war.

HOWEVER, given an initial (right after Pearl Harbor) Japanese "happy time" off the US west coast combined with the fact that you have the anti-Japanese hysteria there, there will be a huge political outcry to do something and remember - this will be before the Germans can get boats across for "Operation Drumbeat". In December 1941 the USA has only so many ships suitable for convoy escort or even yachts convertible for patrol. The only way to get more long range ASW a/c for patrol is to designate more B-17's, B-24's coming off the lines for such work rather than USAAF bombing squadrons (and in 12/41 really talking about B-17's for a quick fix). With greater losses in the Pacific, it spreads the US merchant marine thinner.

To meet a 2 coast sub threat requires the US move some assets from the Atlantic to the Pacific, and shift some production & distribution priorities. It makes the roughly 70/30 split of assets to the "Germany First" effort a more difficult political sell.

Because of the experience with Japanese subs on the west coast, the US wises up with coastal convoys etc & the "happy time" for the U-boats is less happy. However there are fewer ASW assets in the Atlantic than OTL and also fewwer merchant ships (due to losses in the Pacific that need to be made up). Combined with the need to put more assets in the Pacific due to the politics, the buildup in England is slower, Britain is getting a decrease in supplies from the USA. As a result of this, Lend-Lease to the USSR is going to be at a lower level (fewer ships, fewer convoys due to protection issues etc).

To me, the major effect of a Japanese sub campaign against the US merchant marine will not be in the Pacific - at most a few months delay in the timeline - but in Europe.
 
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