6th Fleet (Imperial Japanese Navy)

The 6th Fleet (第六艦隊, Dai-roku Kantai^?) was a fleet of the Imperial Japanese Navy (IJN) that during World War II, had primary responsibility for the command of submarine operations.

The 6th Fleet was formed on 15 November 1940, and was assigned general control of all IJN submarine operations. Its initial mission was reconnaissance off the west coast of the United States, east coast of Australia, and the sea lanes of the Indian Ocean.

Japan had prior to the attack on Pearl Harbor a diverse submarine fleet, some of which had unique distinctions: the only submarines in existence of over 5,000 tons submerged displacement, submarines over 400 feet in length (until the advent of nuclear power), the 41 submarines in its retinue (and of the world) that could carry specially designed aircraft, and submarines with the longest ranges and highest speeds of any nation. With the development of the Type 95 submarine-launched variant of the Long Lance oxygen-propelled torpedo, Japan not only had the world's most advanced torpedo, but one with the largest warhead.

Despite these advantages, IJN submarines achieved remarkably little during World War II primarily having in hindsight suffered from the antiquated strategy of the Imperial Japanese Navy General Staff, who viewed submarines as little more than scouts whose main role was to locate and shadow enemy naval task forces in preparation for a decisive surface conflict. Maybe the IJN General Staff was slow to change as the submarines were generally slow to dive, easy to track with radar and sonar, difficult to maneuver underwater, and less sturdy than their German U-boat counterparts.

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