Which Soviet foreign minister notified Japan that the Soviet Union had declared war in August 1945?

Vyacheslav Molotov notified Japan that the Soviet Union had declared war in August 1945.

On 8 August 1945, Molotov informed Japanese ambassador Naotake Satō in Moscow that the Soviet Union considered itself at war with Japan from 9 August. The declaration broke the Soviet-Japanese Neutrality Pact and fulfilled the Soviet commitment made at the Yalta Conference to enter the Pacific war after Germany's defeat.

The Soviet invasion of Japanese-held Manchuria began just after midnight on 9 August in local time. Soviet forces attacked across several fronts, while Japan was already facing the consequences of the Hiroshima atomic bombing three days earlier. The timing added a major military and diplomatic shock to Japan's leadership.

Molotov was the Soviet foreign minister throughout the wartime alliance with Britain and the United States. He later represented the Soviet Union at major postwar negotiations. The Soviet declaration is sometimes misdated as 9 August because the military invasion began then, but the diplomatic notification occurred on 8 August in Moscow.