Appendices - Hirohito's War
APPENDIX A: SUBMARINES - THE UNDERSEA WAR
The Failure of Japanese Submarine Design: The fate of the three built Sentoku Type (I-401, I-402, I-403), the two Type AM (I-13 and I-14) and the three Sentaka Type (I-201, I-202, I-203) submarines, none of which ever saw action, is symptomatic of the failure of the Japanese submarine strategy in World War II. Japan produced technologically advanced submarines without ever designing a strategy to use them to maximum effect; their submarine strength was constantly dissipated in the pursuit of tasks for which they were not designed.
The I-400 and I-201 classes were in some respects the most advanced submarines built up until that date. The I-400, with its ability to cruise one and half times around the world and launch air strikes anywhere, anticipated the era of ballistic missile submarines first trialed by the Soviet Union in 1955 followed by the development of the first underwater-fired launchers with the USS Washington Class nuclear submarines in the early 1960s. As Dr. Hans Van Tilburg of the National Marine Sanctuaries in the Pacific Islands has observed of the similarly advanced carrier-submarine, I-14, which had also been designated for the Panama Canal mission, “the I-14 predates the cruise missile concept.”6
Meanwhile the I-201 Type anticipated the development of submarines that were genuine underwater craft rather than the typical Japanese and American submarines that were essentially surface vessels that could submerge. With a submerged top speed of 19 knots compared to 15.7 knots on the surface, the I-201 was slower only than the German Walter Type XVII. Tilburg noted that, ‘If you look at a sub like the I-201, it was nothing like anything in World War II… It had a streamlined body and conning tower and retractable guns. It looks more like a Cold War sub.’7
German technology had underpinned the rapid development of Japan’s submarines after World War I. Progress had been significantly aided by the acquisition through war reparations of seven German U-139 Type U-boats, which had almost succeeded in throttling Great Britain’s commercial lifeline. From 1931 Japanese technical abilities advanced to the point that they were able to start designing and building their own marine diesel units which previously they had had to import. Not included in the naval limitations treaties in Washington and then London in 1922 and 1930, the submarine was a maritime weapon that Japan could develop to the maximum. By the time that they entered World War II after the attack on Pearl Harbor, Japan had more varieties of submarine than any other nation; by the end of the war the Japanese fleet included not only aircraft carrier submarines but also miniature submarine carriers, cargo submarines, tankers, scouters, minelayers, midget (kohyoteki) and suicide submarines (Kaiten and Kairyu). Of 56 submarines displacing more than 3,000 tons in World War II, 52 of them were Japanese.
In addition to the profusion of submarines developed, Japan also produced the most destructive and famous torpedo of the war - the Long Lance Type 93. With the potency of their 63 submarines at the outset of the Pacific War, double the number available to the United States, it could have been expected that Japanese submarines would be a major contributor to Japan’s war effort. In the event, it proved to be the most disappointing service of their armed forces. After the war when Admiral Ozawa was interrogated about the poor performance of the Japanese submarine force, he answered that it was because “they did not develop their electrical equipment such as radar, sonic devices, and other equipment to the extent they should have. I think that is the basic reason for our poor showing.”8 Post war analysis was to show that poor electrical equipment was but one component in the failure of Japanese submarine operations.