Japanese submarine I-51
Following World War I, the Imperial Japanese Navy General Staff began to re-consider submarine warfare as an element of fleet strategy. Before the war, the Japanese Navy regarded submarines as useful only for short-range coastal point defense. However, based on the success of the Imperial German Navy in deployment of long-range cruiser-submarines for commerce raiding Japanese strategists came to realize possibilities for using the weapon for long range reconnaissance, and in a war of attrition against an enemy fleet approaching Japan. Procurement for a large, long-range Japanese submarine was authorized in fiscal 1918 under the Eight-six fleet program, under the designation S22.
"Project S22" was based on the latest Royal Navy design, the British K class submarine. Japanese ties to Great Britain via the Anglo-Japanese Alliance were still strong. "Project S22" was laid down at Kure Naval Arsenal on 6 April 1921, launched on 29 November 1921 and completed on 20 June 1924.
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".