Kantai Kessen

The Decisive Battle Doctrine (艦隊決戦, Kantai Kessen, "naval fleet decisive battle") was a naval strategy adopted by the Imperial Japanese Navy prior to the Second World War. The theory was derived from the writings of American naval historian Alfred Thayer Mahan. In the Decisive Battle Doctrine the Japanese navy would win a war by fighting and winning a single, decisive naval action. The idea gained broad acceptance following the Russo-Japanese War, where a well-trained, smaller Japanese naval force gained a decisive victory in the Sea of Japan at the Battle of Tsushima, defeating the Imperial Russian Navy of their rival the Russian Empire, a western naval power^{[citation needed]}. Operational plans thereafter were influenced by the effective naval gunnery Japan demonstrated at Tsushima.^[1]

From the turn of the century up through the start of the Second World War Japanese planners believed achieving victory in such a battle would be dependent upon the effective use of a strong battleship force.^[2] The Japanese triumph at Tsushima led to the naval doctrine of Taikan Kyohō Shugi (大艦巨砲主義), the principle of big ships and gigantic guns.^[3] Imperial Japanese Navy planning envisioned assuming a defensive posture and waiting upon the enemy fleet to approach, then destroying it in a sharp battle off the Japanese mainland.^[3] Japan's victory over the Imperial Russian Navy validated this doctrine in the eyes of the Imperial Japanese Navy General Staff. Thereafter naval procurement and subsequent deployment of naval assets was based upon the Kantai Kessen doctrine.