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|Displacement:||46 tons submerged|
|Length:||23.9 meters (78.5 feet)|
|Beam:||1.8 meters (6 feet)|
|Height:||3 meters (10.2 feet)|
|Ballast:||5899 pounds in 534 11-pound lead bars|
|Designed Depth:||30 meters (100 feet)|
|Propulsion:||one electric motor, 600 horsepower at 1800 rpm, two screws conter-rotating on single shaft, leading prop 1.35 meters diameter, right-handed; trailing prop 1.25 meters diameter, left-handed|
|Batteries:||192 trays of two two-volt cells each, 136 trays forward, 56 trays aft|
|Endurance:||100 nautical miles at 2 knots, 80 nautical miles at 6 knots, 18 nautical miles at 19 knots|
|Speed:||23 knots surfaced, 19 knots submerged|
|Complement:||one commander, one crewman|
|Armament:||two 18-inch torpedoes muzzle-loaded into tubes, one 300-pound scuttling charge (big enough not only to destroy the sub but to disable any ship it was near)|
Twenty ko-hyoteki were built. The "Type 'A' Target" name was assigned as a ruse -- if their design was prematurely discovered by Japan's foes, the Japanese Navy could insist that the vessels were battle practice targets. The first two, Ha-1 and Ha-2, were used only in testing. Ha-19 was used as I-24tou (see below). The other hull numbers are unaccounted for.
I-16tou, commanded by Masaji Yokoyama and crewed by Sadamu Uyeda, radioed on the evening of December 7 a report that the attacks had been successful, and was credited with the sinking of USS Arizona (BB-39). Photographs show what appears to be a ko-hyoteki inside Pearl Harbor firing torpedoes at Battleship Row, and the light cruiser St. Louis (CL-49)[?] reported being attacked by torpedoes just outside the harbor. In October 2002, I-16tou has not yet been located.
I-18tou, commanded by Shigemi Furuno and crewed by Shigenori Yokohama, was depth-charged outside the harbor in Keehi Lagoon[?]. The wreck was discovered in 1960 and raised. Its bow (with its still-dangerous torpedoes) was cut off and resunk, and the rest of the boat shipped to Japan. There, a new bow was fabricated and the boat put on display on Eta Jima[?].
I-20tou, commanded by Akira Hiro-o and crewed by Yoshio Katayama, was ordered to attack from a location closer to Waikiki than any of the other ko-hyoteki. Near their assigned location and before the air attack on Pearl began, the destroyer USS Ward (DD-139)[?] reported firing on a submarine. In late August, 2002, the wreck of a ko-hyoteki was discovered with a three-inch shell hole in its sail. That shell must have killed Hiro-o, making him the very first enemy killed by United States forces in World War II.
I-22tou was rammed and depth-charged during a running battle with destroyers, later raised, and used as landfill with the bodies of commander Naoji Iwasa and crewman Naokicki Sasaki still aboard.
I-24tou (Ha-19) was captured the day after the attack. Its crewman, Kiyoshi Inagake, was killed, and its commander, Kazuo Sakamaki, was made a prisoner of war -- the first for America. The sub was displayed throughout the United States.