Submarines of the Imperial Japanese Navy
Imperial Japanese Navy submarines originated with the purchase of five Holland type submarines from the United States in 1904. Japanese submarine forces progressively built up strength and expertise, becoming by the beginning of World War II one of the world's most varied and powerful submarine fleets.
Japanese submarine tender Chōgei
Under the Eight-eight fleet plan, the Imperial Japanese Navy planned to acquire 100 submarines for long-distance scouting operations, which would also be used to conduct attrition warfare against any enemy fleet approaching Japan. "Chōgei" was intended to serve as a flagship for the Submarine Division Commander and as a depot ship for the nine submarines in a submarine division.