After World War I, Japan ranked third in the world as a naval power and while this added greatly to her international prestige and position it also embroiled her in a naval construction race with her former allies, the United States and Great Britain. The race had begun to accelerate even during the war and heightened international tensions at a time when public opinion was clamouring for an end to competitive armaments production. It placed enormous strains on the economies of those involved, especially Great Britain and Japan. It is therefore important to consider the historical development of Japanese involvement in this naval arms race and also why Japan saw it as advantageous to participate in naval limitation discussions. In order to comprehend the position adopted by Japan before and during the conference, one needs to identify the major pillars in Japanese naval policy which caused Japan to ‘race’ with other naval powers. These were the changing conception of who was the navy’s primary potential enemy, the origins and development of the 8-8 Fleet and the evolution of the so-called 70% ratio in ships, especially vis-à-vis the United States Navy. One needs also to examine research within the Japanese Navy on naval limitation prior to the calling of the conference at Washington in 1921. This will clarify Japan’s position and provide the context in which to place and evaluate the evolution of Katō Kanji’s own thinking on the subject of naval limitation as well as his behaviour at Washington.