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.
Submarines of the Imperial Japanese Navy
Overall, despite their advanced technical innovation, Japanese submarines were built in relatively small numbers, and had less effect on the war than those of the other major navies. The IJN pursued the doctrine of "guerre d'escadre" (fleet vs fleet warfare), and consequently submarines were often used in offensive roles against warships. Warships were more difficult to attack and sink than merchant ships, however, because naval vessels were faster, more maneuverable, and better defended.