Operation August Storm (Battle of Manchuria). On August 9, 1945, the USSR joined the war against Japan in the Far East with the Manchurian operation of the Soviet troops which culminated in capitulation of the 1 million strong Kwantung Japanese Army. As a result of the war Soviet armed forces also liberated the South Sakhalin and the Kurils. On September 2,1945 Japan signed the unconditional capitulation act. Russian soldiers during a combat operation in Manchuria in August 1945.