Vyacheslav Molotov told Japan's ambassador that the Soviet Union had declared war on Japan in 1945.
Molotov delivered the notice to Ambassador Naotake Satō in the Kremlin on August 8, 1945. He stated that the Soviet government would consider itself at war with Japan from August 9, and Soviet forces began their offensive against Japanese-held Manchuria shortly afterward.
The declaration ended the Soviet-Japanese Neutrality Pact before its stated expiration and opened a major front in northeast Asia. It came between the atomic bombings of Hiroshima and Nagasaki and became one of the major pressures on Japan's leadership during the final days before surrender.