How successful were the human torpedoes, developed by the Japanese during the WW2?

it was a great success and the main threat for US Navy
it was a success, over 50 ships were sunk
it was a disappointment
it was never used
Kaitens had a very limited diving depth, which in turn limited the diving depth of the host submarine. This is one of several factors blamed for the very poor survival rate of submarines armed with kaitens: eight submarines being lost for the sinking of only two enemy ships and damaging several others.
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reach: rather globalJapannavysubmarinesweaponryweaponsWorld War II