6th Fleet (Imperial Japanese Navy)
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.
Japanese submarine I-52 (1942)
This class of submarines was designed and built by Mitsubishi Corporation, between 1943 and 1944, as cargo carriers. They were quite long and carried a crew of up to 94. They also had a long cruising range at a speed of . The Japanese constructed only three of these submarines during World War II ("I-52", and ), although twenty were planned. They were the largest submarines ever built at that time, before the enormous "Sentoku" subs were built, and were known as the most advanced Japanese submarines of their time.