As agreed with the Allies at the Tehran Conference in November 1943 and the Yalta Conference in February 1945 , the Soviet Union entered World War II 's Pacific Theater within three months of the end of the war in Europe . The invasion began on 9 August 1945 , exactly three months after the German surrender on May 8 ( 9 May , 0:43 Moscow time )
Yalta Conference
Yalta Conference
Soviet invasion of Manchuria