While the Americans were interested in supporting Kolchak's White government, the Japanese aimed to take over Russian ports and coastal territories.
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 Priamurye Government.
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.
Another major reasons were to rescue the 40,000 men of the Czechoslovak 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 and to protect the large quantities of military supplies and railroad rolling stock that the United States had sent to the Russian Far East in support of the Russian Empire's war efforts on the Eastern Front of World War I.