Far Eastern Front in the Russian Civil War During the Russian civil war , the Far Eastern part of the former Russian Empire was a battleground for violence between the Communists and the remnants of the Whites . The fighting in this front expanded from Outer Mongolia , through Eastern Siberia , and in the Ussuri and Amur districts of Outer Manchuria in Russia . Combatants . The fighting forces on the Communist side were the Red Army , Kuban Cossacks , Communist Mongolian militias , and the Far Eastern Republic . On the White side , there were local White army units , pro - white Mongolian militias , Mongolian government forces , and the Beiyang army . Allied intervention forces arrived which included 70 , 000 Imperial Japanese soldiers and 10 , 000 US Marines . The Japanese Goals . During the Bolshevik revolution , the Japanese were already gaining influence in Chinese Manchuria . They were surprised when the Bolsheviks successfully took power in Russia . While the Americans were interested in supporting Kolchak ' s White government , the Japanese aimed to take over Russian ports and coastal territories . In 1918 Japan occupied Vladivostok with the United States Marines . The Japanese had plans of rapid expansion starting in Amur and Ussuri river region all the way to Lake Baikal . In response to the Russians ' establishment of the Far Eastern Republic , the Japanese backed the Provisional Priamur Government . The American Aims . The United States was interested in helping Admiral Kolchak ' s government in Siberia , which was in need of aid . They wanted to press the Red Army out of Siberia and allow the White Movement to establish control of Russia and defeat the Bolsheviks . A major contributing factor was the United States government fears that communism would spread through the U . S if the Bolsheviks won the civil war . Communist / Bolshevik Response . The Bolshevik effort in the Far East was the same as on the other fronts : to retake or hold on to territory of the former Russian Empire . The goal of the Russian Soviet Federated Socialist Republic ( RSFSR ) was to stop the Allied advance into Siberia . The Soviets set up the Far Eastern Republic as a buffer state to hold off the White and allied armies . Mongolia . The war expanded into Mongolia as White armies in the far east retreated . While others retreated to Japan or China some tried to hold on to Mongolia which was a Czarist puppet state . As the war dragged on , Mongolians were forced to take sides . Some joined the Communists , either by entering their armies or forming militias to help fight the Whites . Others went with the whites , as part of the puppet government ' s forces or militias . The Communists burned Buddhist temples and killed white supporters to terrify Mongolians into joining them , and the Whites used similar tactics . Aftermath . In the aftermath of the civil war was the Whites were forced into exile . The Americans left Siberia and the Russian far east in 1920 . Japan held it even after the Whites were defeated , and would not withdraw until October 1922 . With the war over the Soviet Government in Russia got to keep all of Russia ' s pre - war territories in the far east . Future clashes over territory in the region would continue into the next decade , invasions by Japan in 1938 and 1939 .