This is coolbert:
Various combatants used midget submarines during World War Two [WW2]. With ONLY varying success. A mixed record at best! Again, these midget subs were intended only for a defensive role [Germany], or a special purpose type mission [Britain, Japan]. These were NOT general purpose submarines that could perform a variety of missions. NOT versatile.
* Japanese. Type A,B,C and Type D midgets.
Conceptually, the Japanese approach to midget submarines AT THE START OF WW2 WAS RADICALLY DIFFERENT THAT OTHER COMBATANTS WHO ALSO HAD IN THEIR NAVAL INVENTORY MIDGETS!!
"They were originally intended to be carried by larger Japanese ships and deployed in the path of an enemy fleet, where they would disrupt its operations with torpedo attacks. However, during the Second World War, the midgets were used for special operations against ships in enemy harbors, among them the 7 December 1941 Pearl Harbor attack and May 1942 raids on Sydney, Australia, and Diego Suarez in the Indian Ocean."
Midgets were seen - - by the Japanese - - as an offensive weapon - - for special purpose missions!!
"Carried" [piggy-backed] to the target by another much larger ocean-going [pelagic] submarine. The midget would be deployed near the target and attack, penetrating defenses normally "off-limits" to a conventional submarine. Pearl Harbor, Sydney, Diego Suarez.
The Type D class midgets WERE to be used strictly as defensive weaponry. Coastal-huggers attacking American warships venturing close to the Japanese home islands in 1945.
The extent to which the Japanese put their faith in midgets can be seen by the number of "Koryo" midgets found in a drydock at the end of the war!
* British. X-craft.
"The X class submarines' weapons were two side-cargoes - explosive charges held on opposite sides of the hull with two tons of amatol in each. The intention was to drop these on the sea bed underneath the target then creep away. The charges were set off by a time fuze."
[not even carrying torpedoes. Had "charges" attached to the side of the sub that would be dropped "near" or under the target and detonated with time fuze! These X-craft were specifically developed with destroying or neutralizing German large surface raiders operating out of Norway!?]
"Their first deployment was Operation Source in September, 1943, an attempt to neutralise the heavy German warships based in Northern Norway. Six X-Craft were used, but only 2 successfully laid charges (under the German battleship Tirpitz); the rest were lost, scuttled or returned to base. The Tirpitz was badly damaged and out of action until April 1944."
[as one can surmise, the success rate of these midget subs was not too great!]
* Germany. "Seehund".
"The Seehund (seal) (also known as Type XXVII ) was a successful series of German midget submarines created during World War II. Designed in 1944, and run by two men crews"
"The small size and its rapid movement made the Seehund virtually undetectable and difficult to destroy due to their resilient hulls. The submarines were operated by crews of two and carried two underslung torpedoes."
[again, the total armament is two torpedoes, carried OUTSIDE THE SUB. Fire those two, and back to base!]
The record of midget submarines during WW2 - - is mixed at best!! Was all the effort worth it?