Kaiten

were crewed torpedoes and suicide craft, used by the Imperial Japanese Navy in the final stages of World War II. In recognition of the unfavorable progress of the war, towards the end of 1943 the Japanese high command considered suggestions for various suicide craft. These suggestions were initially rejected, but later deemed necessary. Various suicide craft were developed in the Japanese Special Attack Units. For the Navy, this meant Kamikaze planes, Ohka piloted bombs, Shinyo suicide boats, Kaiten submarines, and Fukuryu suicide divers or human mines. The Kamikazes were somewhat successful, and the second most successful were the Kaitens. Research on the first Kaiten began in February 1944, followed on 25 July of the same year by the first prototype. By 1 August, an order for 100 units had been placed. The very first Kaiten was nothing much more than a Type 93 torpedo engine compartment attached to a cylinder that would become the pilot's compartment with trimming ballast in place of the warhead and other electronics and hydraulics. The torpedo's pneumatic gyroscope was replaced by an electric model, and controls were installed which gave the pilot full control of the weapon. The original designers and testers of this new weapon were Lieutenant Hiroshi Kuroki and Lieutenant Sekio Nishina. They both died at the controls of Kaiten, Lieutenant Kuroki in a very early training prototype. In total six models of Kaiten were designed, Types 1, 2, 4, 5, and 6 were based on the Type 93 torpedo. Type 10 was the only model based on the Type 92 torpedo. Types 2, 4, 5, 6, and 10 were only manufactured as prototypes and never used in combat. Early designs allowed the pilot to escape after the final acceleration towards the target. There is no record of any pilot attempting to escape or intending to do so, and this provision was dropped from later Kaiten, so that, once inside, the pilot could not unlock the hatches. The Kaiten was fitted with a self-destruct control, intended for use if an attack failed or the impact fuze failed.