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.
List of warships sunk during the Russo-Japanese War
Although submarines, torpedoes, torpedo boats, and steel battleships had existed for many years, the Russo-Japanese war was the first conflict to see mature forms of these weapon systems deployed in large numbers. Over a hundred of the newly invented torpedo boats and nearly the same number of torpedo boat destroyers were involved. The Imperial Russian Navy would become the first navy in history to possess an "independent operational submarine fleet" on 1 January 1905. With this submarine fleet making its first combat patrol on 14 February 1905, and its first clash with enemy surface warships on 29 April 1905, all this nearly a decade before World War I even began.