Submarines of the Imperial Japanese Navy
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, 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. During the last two years of the War in the Pacific, many IJN submarines were also occupied serving to transport supplies to isolated island garrisons, ones that had been deliberately bypassed by the Americans and the Australians and which could not be reached by surface transports because of blockade by Allied warplanes and naval vessels.
Japanese submarine I-15
I-15 was a Japanese B1 type submarine. She was completed at Kure Navy Yard on September 30, 1940, whereupon she entered into service with the Imperial Japanese Navy. Her first and only commanding officer was Commander Nobuo Ishikawa. "I-15" operated off the north coast of Oahu during the raid on Pearl Harbor. Her second wartime patrol, in May and June 1942, took her to the Aleutians, where she conducted reconnaissance of several islands. "I-15"s third and final patrol took place from August to November 1942, when she operated in the Solomon Islands in the South Pacific, supporting the Japanese efforts to hold Guadalcanal. One source (Morison) suggests that "I-15" hit the battleship with a torpedo on September 15, 1942. More recent authorities (Hackett & Kingsepp) maintain that the torpedo came from another submarine operating in the area, , which was also responsible for the sinking of , which "I-15" duly observed and reported. On November 10, 1942, a U.S. ex-destroyer (modified to a fast minesweeper), , sank "I-15" at Cape Recherche, San Cristóbal, with all hands lost.
Commander Ishikawa was promoted to the rank of Captain posthumously. On December 14, 1942, more than one month after "I-15" was sunk, sank an unknown submarine which it misidentified as the "I-15".