Submarines of the Imperial Japanese Navy
Imperial Japanese Navy (IJN) submarines formed by far the most varied fleet of submarines of World War II, including manned torpedoes ("Kaiten"), midget submarines ("Kō-hyōteki", ), medium-range submarines, purpose-built supply submarines (many used by the Imperial Japanese Army, see Type 3), fleet submarines (many of which carried an aircraft), submarines with the highest submerged speeds of the conflict ("Sentaka" ), and submarines able to carry multiple bombers (World War II's largest submarine, the Sentoku ). They were also equipped with the most advanced torpedo of the conflict, the oxygen-fuelled Type 95 (which are sometimes confused with the famed Type 93 Long Lance torpedo).
Japanese submarine I-73
"I-73" participated in the attack on Pearl Harbor as part of the 3rd Submarine Squadron in the 6th Fleet of the IJN. It was one of the vessels created as part of Japan's 1st Naval Armaments Supplement Programme in 1931. On 27 January 1942, "I-73" became the first warship to be sunk by a United States Navy submarine; USS "Gudgeon" fired three torpedoes at "I-73" and destroyed it. "Gudgeon" claimed that the torpedoes only damaged "I-73", but Station HYPO confirmed the loss.