In August 1918, the Czechoslovak Legion, under the leadership of Radola Gajda, fought the Red Army for control of the mountain passes around Lake Baikal which were well defended.

[3] News of the Czechoslovak Legion's campaign in Siberia during the summer of 1918 was welcomed by Allied statesmen in Great Britain and France, who saw the operation as a means to reconstitute the Eastern Front against Germany.

U.S. President Woodrow Wilson, who had resisted earlier Allied proposals to intervene in Russia, gave in to domestic and foreign pressure to support the legionaries' evacuation from Siberia.

In early July 1918, he published an aide-mémoire calling for a limited intervention in Siberia by the U.S. and Japan to rescue the Czechoslovak troops, who had been blocked by Bolshevik forces in Transbaikal.

The Allied intervention in Siberia continued so that by autumn of 1918, there were 70,000 Japanese, 829 British, 1,400 Italian, 5,002 American and 107 French colonial (Vietnamese) troops in the region.