The Mk-15 was developed from 1936 onwards, and was in wide-spread service by 1941. It saw no major action in combat until Guadalcanal, but four of these weapons were used to scuttle the carrier Lexington at the Battle of the Coral Sea. In October 1942, sixteen torpedos were fired from two destroyers to scuttle the carrier Hornet, but they failed to sink the carrier - it is not clear how many detonated in the first place, and how many detonated below or against the carrier. The problem with the Mk-15, as with the Mk-14, was the Mk-6 exploder, which employed a magnetic detector to detonate under the target - in theory. In praxis, it didn't. See the article on the Mk-6 for details.

    Thanks to this, the Mk-15 accounted for no single Japanese vessel through all of 1942. However, in 1943, the destroyers although the major un-detonator related problem (deep running) had not been detected, the Mk-6 was deactivated and the contact exploder substituted, which change resulted in destroyers becoming weapons of offence instead of defence again. In the battles of Vella Gulf and Cape St. George, destroyer attacks using torpedos sank six enemy destroyers without loosing a single man, with a fifth (the legendary Shigure) escaping only because a torpedo hitting her rudder failed to explode. 
U.S. destroyer torpedos also accounted for the only "dreadnought"-type battleship ever sunk in action by surface launched torpedos, the Fuso, during the Battle of Surigao Strait.

    On the whole, the Japanese torpedo, Type 93, the famous "Long Lance", was a far superior weapon. It was faster, carried more explosives, had a longer range and, since it was oxygen-driven, was more difficult to spot.