With the end of World War I, both the United States and Japan launched massive naval build-up programs. Under the Daniels Plan, the U.S. sought to build sixteen new battleships, while Japan launched the so-called 8-8 Fleet Program, under which eight battleships and eight battlecruisers were to be built. These programs however, were to be extremely heavy burden on the financial resources of both countries. The estimate was that the U.S. would spend 11% and Japan roughly one-third, of their respective national budget on those fleet-building programs.

It was under such circumstances that both countries jumped at the British initiative that a naval disarmament conference be convened. The 1921 - 1922 Washington Conference resulted in a ratio of 5:5:3 in the capital ships and in the aircraft carriers of the United States, Britain and Japan respectively.

The Japanese at first demanded parity, and then sought 10:10:7 but ultimately failed in gaining her objective. It was clear that, with her limited resources, Japan would never win in a free warship building competition with the United States.

Both the US Navy and the I.J.N. had the identical scenario about a future Pacific War. Japan would attack and occupy the Philippines in the initial phase of the war. The United States would send its battle squadron westward across the Pacific to rescue the Philippines and to engage the main element of the Japanese Fleet.

Under such a scenario, the result of numerous war games showed that I.J.N. had to have at least 70% of the invading US battleship strength to take a viable opposing stand. What I.J.N. planned, at this juncture, was to make maximum use of its forward bases in the Pacific, and to decimate the U.S. Fleet during its westward march through the use of aircraft, light torpedo forces and submarines. This was called ‘ZENGEN-SAKUSEN’ (Tactics of Gradual Attrition).

In the early 1930’s I.J.N. perfected the surface launched Type 93 oxygen torpedo. This 24-inch torpedo (later dubbed ‘LONG LANCE’) could travel 24 miles at 36 knots. With this weapon, a destroyer theoretically outranged a battleship. The 21-inch submarine version was called Type 95 and was adopted a few years later.