As a result of World War I, Japan, the United States and Great Britain came to be referred to as the three great powers. The [former German] equatorial Pacific Islands lying between the U.S. territories of the Philippines and Guam and the U.S. mainland became mandated territories of Japan. From way back, Britain had acquired various rights and interests in China with Singapore and Hong Kong serving as its footholds. Seeking Anglo-American support, China subsequently tried to reduce Japan’s vested rights in China. Intensification of the confrontation between Japan and the United States and Britain was inevitable. In 1922, the Anglo-Japanese Alliance was annulled and in the same year Japan discontentedly signed the Washington Naval Treaty, followed by the London Naval Treaty of 1930. In 1931, the Manchurian Incident occurred, which led to Japan’s withdrawal from the League of Nations in 1933.
These developments were followed by the North China Incident in 1937 (later renamed the China Incident). In the meantime, the Soviet Union and Germany had been building up their national strength and, in November 1936, Japan concluded the Anti-Comintern Pact with Germany. The China Incident steadily assumed more serious proportions, at first particularly through British interference. However, when Germany annexed Austria and occupied Czechoslovakia in 1938, tensions rose in Europe and it now became the United States rather than Britain, which gave active support to China.