The Soviet Union began its offensive against Japan in Manchuria on August 9, 1945.
The Soviet Union declared war on Japan on August 8, Moscow time, and its forces began their invasion shortly after midnight on August 9 in the region. The offensive attacked Japanese forces in Manchuria from several directions and rapidly disrupted Japan’s strategic position in northeast Asia.
The timing was especially important because it coincided with the day of the atomic bombing of Nagasaki. Japanese leaders therefore faced multiple shocks: continued American bombing, the Soviet attack, and the possibility that the Soviet Union would no longer serve as a possible intermediary in negotiations.
The Soviet offensive continued through the final weeks of the war and included operations in Manchuria, southern Sakhalin, and the Kuril Islands. Japan announced its acceptance of the Potsdam Declaration on August 15, but fighting continued in some areas until September. The Soviet campaign is also known as the Soviet–Japanese War of 1945.