Ha-7-class submarine
The was an early class of submarines of the Imperial Japanese Navy. It was also called the "Vickers C-3 class". Background. A final two vessels of the British C-class submarine design were built completely in Japan by the Kure Naval Arsenal as part of the emergency expansion of the Imperial Japanese Navy due to World War I. Although the design was considered obsolete by this time, these vessels were felt necessary to meet the perceived threat of German submarine activity in Japanese coastal waters. Physically almost identical to the "Ha-3" class, the two vessels incorporated a  number of improvements, including a change in the location of the rudder for better control, and the addition of two externally mounted torpedo tubes to double the attack capability from previous designs. Arriving in Japan during the closing stages of the war, neither vessel was ever used in combat.