1919-1938

In 1918, Japan continued to extend its influence and privileges in China via the Nishihara Loans. Following the collapse of the Russian Empire in Bolshevik Revolution, Japan and the United States sent forces to Siberia in 1918 to bolster the armies of the White Movement leader Admiral Aleksandr Kolchak against the Bolshevik Red Army. In this Siberian Intervention, the Imperial Japanese Army initially planned to send more than 70,000 troops to occupy Siberia as far west as Lake Baykal. The plan was scaled back considerably due to opposition from the United States.

In July 1918, President Wilson asked the Japanese government to supply 7000 troops as part of an international coalition of 25,000 troops planned to support the American Expeditionary Force Siberia. After heated debate in the Diet, the administration of Prime Minister Terauchi Masatake agreed to send 12,000 troops, but under the command of Japan, rather than as part of an international coalition.

Once the political decision had been reached, the Imperial Japanese Army took over full control under Chief of Staff General Yui Mitsue, and by November 1918, more than 70,000 Japanese troops had occupied all ports and major towns in the Russian Maritime Provinces and eastern Siberia.

In June 1920, America and its allied coalition partners withdrew from Vladivostok after the capture and execution of White Army leader Admiral Aleksandr Kolchak by the Red Army. However, the Japanese decided to stay, primarily due to fears of the spread of communism so close to Japan, and Japanese controlled Korea and Manchuria. The Japanese army provided military support to the Japanese-backed Provisional Priamur Government based in Vladivostok against the Moscow-backed Far Eastern Republic.

The continued Japanese presence concerned the United States, which suspected that Japan had territorial designs on Siberia and the Russian Far East. Subjected to intense diplomatic pressure by the United States and Great Britain, and facing increasing domestic opposition due to the economic and human cost, the administration of Prime Minister Kato Tomosaburo withdrew the Japanese forces in October 1922.