Which Soviet declaration helped pressure Japan during the final days before its 1945 surrender?

The Soviet declaration of war on Japan helped pressure Japan during the final days before its 1945 surrender.

The Soviet Union declared war late on August 8, 1945, and Soviet forces invaded Japanese-held Manchuria shortly after midnight on August 9. This violated the existing Soviet-Japanese Neutrality Pact, which was still formally in effect at the time.

Japanese leaders had hoped the Soviet Union might mediate a negotiated peace with the Western Allies. The Soviet attack destroyed that diplomatic strategy and opened a major front in northeast Asia.

The declaration came between the atomic bombings of Hiroshima and Nagasaki. Historians continue to debate the relative importance of the bombings and Soviet entry in Japan’s decision, but both events formed part of the rapidly changing military and political situation that preceded surrender.