Soviet forces invaded Japanese-occupied Manchuria on August 9, 1945.
The offensive targeted Manchukuo, Japan’s puppet state in Northeast China, as well as nearby Japanese positions in Inner Mongolia and Korea. The Soviet Union declared war on Japan late on August 8, and the invasion began shortly after midnight on August 9.
The campaign rapidly overwhelmed the Kwantung Army, which had once been one of Japan’s most powerful overseas forces. Soviet attacks came from multiple directions and used large numbers of troops, tanks, artillery pieces, and aircraft.
The invasion occurred between the atomic bombings of Hiroshima and Nagasaki and became an important factor in Japan’s decision to surrender. Fighting and regional operations continued after the August 15 announcement, with the formal surrender taking place on September 2.