After the fall of the Tsarist regime and the later provisional regime in 1917, the new Bolshevik government signed a separate peace treaty with Germany. After this the Russians fought against themselves in a multi-sided civil war.

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. Prime Minister Terauchi Masatake agreed to send 12,000 troops, but under the Japanese command rather than as part of an international coalition. The Japanese had several hidden motives for the venture; one was an intense hostility and fear of communism, second a determination to recoup historical losses to Russia and lastly the perceived opportunity to settle the "northern problem" in Japan's security by either creating a buffer state or through outright territorial acquisition.

By November 1918, more than 70,000 Japanese troops under Chief of Staff Yui Mitsue had occupied all ports and major towns in the Russian Maritime Provinces and eastern Siberia.

In June 1920, the United States 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. Japanese casualties from the expedition were 5000 dead from combat or illness, with the expedition costing over 900 million yen.

?