The Decisive Battle Doctrine (艦隊決戦, Kantai Kessen; "fleet showdown") 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.

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. 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. 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. 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.

The Imperial Japanese Navy General Staff was heavily influenced by the writings of the American naval historian Alfred Thayer Mahan. Mahan's writings, including The Influence of Sea Power Upon History, 1660-1783 published in 1890 and The Influence of Sea Power upon the French Revolution and Empire described how British naval power in the Age of Sail had made the British Empire dominant over its rivals and kept it secure. These works were influential in the naval staffs of many nations. Translated into Japanese, they were read at the Imperial Japanese Naval Academy and Naval Staff College. As Britain and Japan were both island nations, the Japanese Navy General Staff felt the British maritime experience was useful and relevant to the future of Japan.

In his writings, Mahan asserts that success in war for the United Kingdom had been dependent upon her control of seaborne commerce. By denying use of the sea lanes to its opponents, Britain had been able to stifle the economies of its enemies, leading to eventual victory. Mahan shows how Britain had made use of a fleet of ships of the line to establish command of the sea. He asserts that the objective of a strong sea power was to build a fleet capable of destroying the enemy's main force in a single battle. By concentrating their ships into a powerful force the British were able to win a decisive victory. Once accomplished, Britain was at liberty to blockade her enemy's ports. Concentration was a key element. Mahan believed that fleet concentration was the most important principle in naval warfare.

In 1896 the Japanese introduced a naval expansion plan. Japan began building battleships, and the four battleships to be built under the plan were to be more powerful in armament and armor than any other warships afloat. This effort to provide the Japanese navy with a qualitative advantage over other naval powers became a hallmark of Japanese planning.

With the onset of World War I, Britain called upon Japan to honor their commitment in the Anglo-Japanese Alliance. Japan did so, joining the Allies. They attacked and took the German colony Tsingtao in China and later performed convoy duties in the Mediterranean. and Pacific eg escorting ANZAC troopships (see Japanese cruiser Ibuki (1907)). At the end of the war Japan gained the German possessions in China, and through the South Seas Mandate Japan gained Pacific islands in Palau, the Marianas, Micronesia and the Marshalls.

Japan's primary goal after World War I was to expand its economic influence and control in East Asia, principally China. In that strategic aim Japan faced opposition from Britain and the Netherlands, who held colonial interests in the region, and from the United States, which sought to protect its territories in Guam and the Philippines, and maintain an economic Open Door Policy in China. In this setting, the naval planners of both Japan and the United States began working out scenarios for how a possible conflict in the Pacific would be fought and won.

The Pacific Ocean, with its vast reaches, was a significant obstacle to overcome. In considering a war in the Pacific against the United States, the Japanese counted on the fact that the size of the Pacific Ocean would in itself be a defense. For the United States Navy to conduct operations against the Japanese, all actions would necessarily be far from their home ports. Travel to the area of combat would consume the fleet's supplies of fuel and food and would limit the amount of time US Navy assets could operate in the western Pacific. Japan could assume a defensive posture and await the US battle fleet. Japanese naval theoreticians, led by Admiral Satō Tetsutarō, argued that a war against the US Navy fought in a single decisive action could be won by Japan.