On 6th February 1922 the Washington Naval Conference was concluded. Among the resolutions there was a division of sea powers into 3 categories and limitation of warships production. The fleet of Great Britain and United States were in the first category. The total load displacement of aircraft carriers of each of those countries were 135 thousand tons. Japan found itself in the second category, its total load displacement of aircraft carriers were 81 thousand tones. In the last category there were France and Italy with 60 thousand tones for each country. Moreover it was prohibited to install cannons bigger than 203 mm. The treaty was effective until 31 December 1936.