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).
Submarine aircraft carriers of Japan
Submarine aircraft carriers were developed by the Imperial Japanese Navy to a greater extent than any other navy, before and during World War II. In total, 42 were built, as listed below (other sources say 47). Although other navies had experimented with submarine aircraft carriers, by World War II the IJN was the only navy (aside from one fielded by the French Navy) using them. They had little effect on the war, although two were used to carry out attacks on the continental United States.