American Expeditionary Force, Siberia

One major reason was to rescue the 40,000 men of the Czecho-Slovak Legion, who were being held up by Bolshevik forces as they attempted to make their way along the Trans-Siberian Railroad to Vladivostok, and it was hoped, eventually to the Western Front.

At the time, Bolshevik forces in Siberia controlled only small pockets, and President Wilson wanted to make sure that neither Cossack marauders nor the Japanese military would take advantage of the unstable political environment along the strategic railroad line and in the resource-rich Siberian regions straddling it.

[1] Concurrently and for similar reasons, about 5,000 American soldiers were sent to Arkhangelsk (Archangel), Russia by Wilson as part of the separate Polar Bear Expedition.

[4] Unlike his Allied counterparts, General Graves believed their mission in Siberia was to provide protection for American-supplied property and to help the Czechoslovak Legion evacuate Russia, and that it did not include fighting against the Bolsheviks.

Repeatedly calling for restraint, Graves often clashed with commanders of British, French, and Japanese forces, who also had troops in the region and who wanted him to take a more active part in the military intervention in Siberia.

[5] American socialist author Upton Sinclair,[4] in his novel Oil!, references the AEF in Siberia and ascribes capitalist motives as the primary driver of the Allied intervention.