Which event did the Soviet Union announce against Japan on August 8, 1945?

The Soviet Union announced a declaration of war against Japan on August 8, 1945.

Soviet Foreign Minister Vyacheslav Molotov informed Japan’s ambassador in Moscow that the Soviet Union would consider itself at war with Japan beginning August 9. Soviet forces then invaded Japanese-held Manchuria shortly after midnight on August 9.

The announcement ended the Soviet-Japanese Neutrality Pact before its stated period had fully run its course. Soviet leaders had previously promised the Western Allies that they would enter the war against Japan after Germany’s defeat. The Soviet offensive attacked Japanese forces across Manchuria and other territories in northeast Asia.

The Soviet entry added a major military and diplomatic shock during the same week as the atomic bombings. Japanese leaders faced pressure from both the United States and the Soviet Union. The combination contributed to the decision to accept the Potsdam Declaration and surrender.