Allied Submarines in The Pacific War - War of Attrition

War of Attrition

After the Battle of Coral Sea, the U.S. Navy detached eight submarines to finish off the damaged aircraft carrier Shōkaku, but she evaded all of them. At the Battle of Midway, although the attack on the battleship Kirishima by USS Nautilus had been unsuccessful, it drew the destroyer Arashi temporarily away from the main fleet to drop depth charges, and the destroyer's return was traced by USS Enterprise's VB-6 to the Japanese task force, where the dive bombers promptly sank four fleet carriers. Overall in 1942, U.S. submarines had only managed to sink the heavy cruiser Kako and the light cruiser Tenryū.

As a result of several key improvements the previous year, U.S. submarines inflicted tremendous losses to the heavy units of the Imperial Japanese Navy in 1944. They destroyed the Japanese fleet carriers Shōkaku and Taihō in the Battle of the Philippine Sea, and sank or disabled three Takao-class cruisers at the start of the Battle of Leyte Gulf. Also sunk that year were the battleship Kongō (being the only Japanese battleship lost to a submarine) and the carrier Shinano, the latter being the largest vessel ever lost to submarine torpedoes.

From 1943, Allied submarines waged an increasingly effective campaign against Japanese merchant shipping and the IJN. By the end of the war in August 1945, the Japanese merchant marine had less than a quarter of the tonnage it had in December 1941. Overall, U.S. Navy submarines sank around 1300 Japanese merchant ships, as well as roughly 200 warships. Despite the need to maintain sea lanes for its empire, the Japanese never successfully developed a cost-effective destroyer escort better suited for convoy duties, while it also did not have the industrial-military complex to replace the losses of its heavily-armed destroyers, nor of its ill-protected merchantmen. By contrast, after the U.S. revealed the weaknesses of Japan's depth charges in 1943, Japanese anti-submarine warfare grew in effectiveness, particularly after the debut of radar in the IJN.