Appendices - Hirohito's War
APPENDIX A: SUBMARINES - THE UNDERSEA WAR
Japanese Submarines Disappointing ‘Kill’ Performance: Perhaps most surprising in the strategic direction of Japan’s submarine force, given the long distances over which the US needed to supply its forces as well as the scale of the matériel required, was that no concerted attempts were made to develop a strategy for the interdiction of the American supply chain. As Commander Fujimori’s plan to attack the Panama Canal indicated, there were officers within the Imperial Naval General Staff who at least understood the possibilities of disrupting US logistics. But, the omission of a consistent plan to disrupt US supply lines was astonishing.
During the course of the war, Japan’s submarine fleet recorded just 184 merchantmen sunk with a total tonnage of 0.9m tons. By comparison German U-boats sank 2,840 ships with an aggregate tonnage of 14.3m tons. The Americans, who started the war with a submarine fleet significantly inferior to that of Japan, sank 1,079 ships with a total tonnage of 4.65m tons while the British sank 493 ships with a total tonnage of 1.52m tons. In hindsight it seems remarkable that the Japanese submarine fleet did not prey on the vast commercial traffic as it approached Hawaii, New Zealand and Australia in the Pacific or indeed India where convoys brought supplies to sustain not only the British but also the Chinese armies. (See Appendix B: Oil, Raw Materials and Logistics.) A concerted effort to disrupt these supply lines in 1942 and 1943 would surely have reaped considerable dividends in the early stages of the ground battles in the Solomon Islands and New Guinea.
Having started the war with a considerable force of 63 submarines to which were added 111 completed during the course of the Pacific War, the Japanese Navy was not short of resources, at least not in the early stages of the conflict before losses and shortage of diesel began to take their toll on operational effectiveness. Out of a total of 128 total Japanese submarine losses, 29 were sunk in 1943 and 58 in 1944.
In part, the failure of Japanese submarines was because the Imperial Japanese Navy failed to develop a merchantman-killer that could be built cheaply and quickly on a mass-produced scale, as Germany achieved with the VII Type U-boat and America managed with the Gato Class. The most produced Japanese type was the Kaichu, which was categorized as a 2nd Class submarine; just 20 units were produced. Japan also produced 20 units of the B-1 Type, which was a 1st Class submarine; but at 356ft long and carrying a single plane it was far from being a low cost and fleet footed merchantman-killer. By comparison the United States built 77 Gato Type submarines and 128 of its updated successor, the Balao Type. Germany’s Kriegsmarine produced 703 VII Type U-boats which at just 220ft in length and 20ft in beam was by far the most successful merchantman-killer of World War II. As Churchill commented, “the only thing that ever really frightened me during the war was the U-boat peril.”18 In the Battle of the Atlantic, the U-Boat threatened the United States and Britain with defeat; Japanese submarines never remotely posed a similar threat in the Pacific. It can only be speculated on how different the outcome of the war might have been if the Imperial Japanese Navy had adopted a submarine strategy similar to that of Germany.
As late as mid-1943 Japan was laying submarine hulls that were highly advanced, technologically complex designs. I-400, I-14 and I-201 took over a year to build and test. Apart from I-13, which was sunk on its way to Truk, none of nine submarines from this group ever saw action. It was an effort that wastefully dissipated Japan’s limited industrial capacity. At the end of 1944, ever hopeful that they could “pull a rabbit out of the hat” with a new weapon that would win them the war, the Imperial Japanese Navy, virtually denuded of surface ships, pinned its hopes on yet another new submarine weapon development at the end of 1944.