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Full blown war on mainland of China between China and Japan was already happening in 1937. The US economic sanctions against Japan and embargos did not happen in a vacuum. As early as 192o's military expansionist policy was already understood that the United States and Japan were on a collusion course. Note The Washington Naval Conference 1921-22
Between 1921 and 1922, the world's largest naval powers gathered in Washington for a conference to discuss naval disarmament and ways to relieve growing tensions in East Asia.

In 1921, U.S. Secretary of State Charles Evans Hughes invited nine nations to Washington to discuss naval reductions and the situation in the Far East. Great Britain, Japan, France and Italy were invited to take part in talks on reduction of naval capacity, and Belgium, China, the Netherlands and Portugal were invited to join in discussions on the situation in the Far East. Three major treaties emerged out of the Washington Conference: the Five-Power Treaty, the Four-Power Treaty, and the Nine-Power Treaty.

The Five-Power treaty, signed by the United States, Great Britain, Japan, France and Italy was the cornerstone of the naval disarmament program.