Prior to WWII, the Soviets and Japanese had already faced off in 1939. The most famous of this Eastern conflict was the Battles of Khalkhin Gol in Mongolia (a Soviet protectorate and ally) near the border with Manchuria, a Japanese-propped "puppet" state. In terms of WWII, practically none of the fighting with the Japanese began for the Soviets until the Red Army had taken back all of its territories from the Nazis (and then some) as well as conquered Berlin itself.
At that point, maintaining his promise to the Allies, Stalin turned his attention to the East. It has been suggested by many historians that Stalin also had an interest in expanding the USSR into more areas of the Eastern borderlands and had designs on portions of an already divided China, particularly Manchuria which the Red Army invaded. Though direct conflict with the Japanese did not start until 1945, the Red Army was a significant factor in winning the War in the Pacific. Soviet forces met little resistance they could not overcome and after the US atomic bombs were dropped on Hiroshima and Nagasaki, Japanese Emperor Hirohito announced his county's surrender on August 15, 1945.
Nonetheless, the Soviet Union had suffered greatly during the war with over 20 million men, women and children killed as a direct result of The Great Patriotic War. Casualties suffered as an indirect result of the war - namely millions who were relocated, imprisoned and executed by Stalin and his private "secret service" the NKVD - will be discussed elsewhere.
|This painting depicts Communist Chinese troops and the capture of the Presidential Palace in Japan after the end of WWII.|