6th Fleet (Imperial Japanese Navy)

[1] 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.

With the outbreak of general war, the mission of the 6th Fleet expanded to include shipping interdiction and mine laying.

The 6th fleet cooperated briefly with the Kriegsmarine (German navy) in the Indian Ocean in operations to interdict British commerce from its base in Penang, but these missions were few.

[3] The success of 1942 was difficult to repeat in forthcoming years with the vast scale of the World War II Pacific conflict, which made it difficult for a submarine to be in "right place at the right time" to make a successful attack,[citation needed] and the increased anti-submarine attention and capabilities by the US Navy.

The increased vigilance of the US Fleet during the Battle of the Philippines, and until of the war, relegated IJN submarine use largely as carriers for kaiten suicide missions.