 In 1931, the Japanese Navy developed the Type 91 torpedo, intended for a torpedo bomber to drop from a height of and a speed of .In 1936, the torpedo was given wooden attachments to the tail, nicknamed the "Kyoban", to increase its aerodynamic qualities—these attachments were shed upon hitting the water.By 1937, with the addition of a breakaway wooden damper at the nose, the torpedo could be dropped from and a speed of .