A midget submarine is any submarine under 150 tons, typically operated by one or two but up to 6 or 8 crew, with no on-board living accommodation. Midget submarines normally work with mother ships, from which they are launched and recovered, and which provide living accommodation for the crew and other support staff.
Both military and civilian midget submarines have been built and operated. Military types work with surface ships and submarines as mother ships. Civilian and non-combatant military types are generally called submersibles, and normally work with surface ships.
Type A Ko-hyoteki-class midget submarines were used in the 1941 attack on Pearl Harbor, in which the type 97 torpedo was used operationally. One of these five midget submarines was shot and sunk by the USS Ward as it was spotted trying to enter Pearl Harbor. The wreckage of the submarine was located by NOAA's Hawaii Undersea Research Laboratory (HURL) in August 2002. Photographic analysis conducted by the United States Naval Institute in 1999 indicates one of the five Ko-hyoteki-class submarines managed to enter Pearl Harbor, and successfully fired a torpedo into the USS West Virginia. The submarine's final resting place is unknown.
Type B Midget Ha 45 prototype built 1942 to test Type A improvements.[5]
Type C Midget Ha 62-76 similar to Type A with crew of 3 and radius increased to 350 miles at 6 knots surfaced or 120 miles at 4 knots submerged.[5]
Type D Koryu (115 completed) improved Type C with crew of 5 and radius increased to 1000 miles at 8 knots surfaced and 320 miles at 16 knots submerged.[6]
X class were used to attack German warships in the North of Norway. One notable target of a successful attack was the battleshipTirpitz. The submarines had a crew of three (plus a diver) and carried two large mines containing Amatol – one on each side. Their strategy was to lay mines on the sea bottom beneath the target, set a time fuse, and exit.
