Which Soviet action on August 8, 1945, helped change Japan’s strategic situation before its surrender?

The Soviet Union’s declaration of war on Japan on August 8, 1945, changed Japan’s strategic situation before its surrender.

The Soviet government declared war late on August 8, Moscow time, and Soviet forces began the invasion of Japanese-held Manchuria shortly afterward. The offensive became the Soviet–Japanese War, also known as the Soviet invasion of Manchuria.

Japan had hoped that the Soviet Union might help mediate a negotiated settlement because the two countries were still formally bound by the Soviet–Japanese Neutrality Pact. The declaration ended that diplomatic hope and opened a powerful front in northeast Asia.

The Soviet invasion occurred between the Hiroshima bombing on August 6 and the Nagasaki bombing on August 9. Historians continue to debate the relative importance of the atomic bombings and Soviet entry, but both events formed part of the crisis that produced Japan’s capitulation.