Question: when did the soviet union declared war on japan and invade manchuria
Answer: The Soviet -- Japanese War ( Russian : Советско - японская война ; Japanese : ソ連 対日 参戦 , `` Soviet Union entry into war against Japan '' ) was a military conflict within the Second World War beginning soon after midnight on August 9 , 1945 , with the Soviet invasion of the Japanese puppet state of Manchukuo .