Andy H wrote: ↑
21 Apr 2020 16:00
You've just highlighted the issue in that the Japanese sank more 'big warships' than the Germans (42-45). The IJN Subs were wedded to the big fleet actions, either recce or support of and found little profit/honour going after merchant ships. Both Kingfish and Takao have mentioned the other aspects that made the IJN subs returns so poor.
The "honor" aspect is a Western myth. Pre-War Japanese naval strategists had realized that the US was a self-sufficient nation and that commerce warfare would neither defeat the US, nor hamper it's ability to prosecute A war with Japan. Also, they realized that the US could rapidly replace their merchant vessels, while replacing warships would require some time. Hence, they focused on warships as targets. While a respectable strategy, it does not take into account on how a commerce war might slow the US march across the Pacific. But, again, the Japanese were banking on a short war, not one of attrition.
Andy H wrote: ↑
21 Apr 2020 16:00
From the book I mentioned earlier:-
The formidable undersea arm of the IJN operated aimlessly and without a coherent strategy in the opening months of 1942. Inflexible pre-war battle objectives usually held sway, or any new ones were often ill-conceived......In the battles of the Coral Sea and Midway the submarine force again failed to measure up to prewar expectations, but the Navy high command continued to hold that submarines should be chiefly used to assist in the decisive battle of capital ships (which they were totally unsuited for)….The highly dispersed operations characterized much of Japanese strategic and operational activity during the war. The occasional entreaty advocating concentration against enemy sea LoC and extended US supply lines, particularly to the South Pacific and Australia, was always played down and usually rejected.
If you look deeply at the matter, the IJN submarine force was not so formidable - it was composed of a mixed bag of long-range & short range subs, as well as a mix of old & new submarines, besides it being a mix of submarines suited for a variety of purposes, but unable to focus on one task.
While their early war strategy was not "aimless", it was some what incoherent, with submarines being sent out for reconnaissance, mining, midget submarine, and attack sorties. However, this can be said also of Kido Butai, as the Japanese tried to find a suitable mission for it after Pearl Harbor.
While the submarines were to have a place in the Decisive Naval Battle, unlike the battleships, the submarines were not held in reserve. Instead, they were sent on various sorties all over the Pacific. At Coral Sea, the submarines did not figure much in the battle, because they were otherwise occupied elsewhere. A few were belatedly sent after the American carriers, but they never found them.
At Midway, the more modern aircraft carrying submarines were sent north to the Aleutians, instead of scouting for th he American carriers. While the older submarines were sent to Midway to form the ticket lines. True to form, the older submarines arrived late & missed the US carriers.
Striking merchant shipping was always advocated, however there were always to few submarines to go around for the tasks at hand. As such, even the more important ones could not be concentrated on. Further, given the IJN submarines' lack of locating targets, had they been concentrated on SLOCs, they probably would not have been successful.