The individual kaiten torpedo was to be lashed to the deck of a submarine and transported under water to the approximate location of a U.S. ship or naval anchorage. Following the appropriate ceremony, the pilot would leave the submarine and enter the kaiten while it was submerged. The kaiten would then be released and propelled at high speed by its oxygen-fueled engine to smash into the enemy ship. Capable of sustaining a speed of 40 knots for one hour, the kaiten could outrun any American warship. There was no provision for the kaiten to be recovered by the launching submarine. Although the Japanese Naval General Staff had insisted that a means be provided for the pilot to be ejected from the kaiten about 150 feet from impact, no pilot is known to have attempted to escape from his speeding torpedo as it approached the target. The first group of kaiten pilots began training in August 1944, and several submarines were modified to carry the submersibles. All kaiten pilots were volunteers.
The first kaiten mission occurred in November 1944 when three submarines, each carrying four kaiten, departed Japan to attack U.S. fleet anchorages in the Caroline Islands. The kaiten were launched on the morning of 20 November. Although three could not get under way because of mechanical difficulties, five others set off for anchored U.S. warships in Ulithi Lagoon. Explosions followed, with the Japanese later claiming three aircraft carriers and two battleships were sunk. In reality, one U.S. tanker, the Mississinewa, was sunk. One submarine, still carrying her four kaiten, was detected by U.S. warships and sunk.
More kaiten missions followed. A kaiten unit composed of three submarines sailed for Iwo Jima on 22 February 1945. One was sunk by the U.S. destroyer escort Finnegan, which was escorting a convoy from Iwo Jima to Saipan when it happened on the Japanese submarine. The surviving submarines inflicted no damage on the U.S. anchorage at Iwo Jima.
The last kaiten operation saw six submarines sortie between 14 July and 8 August 1945, each carrying five or six kaiten. Again, mechanical problems plagued the operation, and three submarines had to turn back to Japan. The kaiten from the others attacked U.S. ships off Okinawa in the most successful of the suicide missions. On 24 July, a kaiten from I-53 sank the destroyer escort Underhill, with a loss of 114 officers and men.
The kaiten effort had failed. Only two U.S. ships had been sunk, one each on the first and the last kaiten missions, but eight of the carrying submarines were sunk, with almost 900 crewmen lost. The kaiten, as with the kamikaze pilots, were an indication that the Japanese had run out of alternatives to counter the rapidly advancing Allied forces on their march toward Japan.
James H. Willbanks
Boyd, Carl, and Akihiko Yoshida. The Japanese Submarine Force and World War II. Annapolis, MD: Naval Institute Press, 1995.; Jentschura, Hansgeorg, Dieter Jung, and Peter Mickel. Warships of the Imperial Japanese Navy, 1869–1945. London: Arms and Armour Press, 1977.; Kemp, Paul. Underwater Warriors. Annapolis, MD: Naval Institute Press, 1996.