Ko-hyoteki Midget Submarine

The Ko-hyoteki (甲標的, "Target A") was a class of midget submarine developed by the Imperial Japanese Navy from the mid-1930s. The Type A measured 23.9 meters in length with a maximum diameter of 1.85 meters and a displacement of 46 tons. It was powered by a 600 HP electric motor providing a maximum underwater speed of 19 knots, with a range of 80 nautical miles at 6 knots or 18 nautical miles at 19 knots. Crew consisted of two men.

Armament consisted of two 450mm torpedo tubes fitted with Type 97 oxygen-powered torpedoes in the bow.

Five Ko-hyoteki participated in the Pearl Harbor attack on December 7, 1941, launched from I-class submarines off Oahu. All five were reported as missing in action, though their ultimate fates remain subjects of historical debate. The crews of these five submarines were posthumously honored as "Nine War Gods" (九軍神), though only nine of the ten crewmen died — one, Kazuo Sakamaki, was captured and became the first Japanese prisoner of war taken by the United States.

Ko-hyoteki were also used at Sydney Harbour (May 1942), Diego Suarez (May 1942), and Guadalcanal. About 50 Type A boats were built; counting the prototypes and the improved Type B and Type C, roughly 100 Ko-hyoteki were completed, apart from the much larger Type D (Kōryū). A surviving example is displayed at the Naval History Museum at Etajima (海軍兵学校).