Which country declared war on Japan on August 8, 1945, shortly before the Nagasaki bombing?

The Soviet Union declared war on Japan on August 8, 1945, shortly before the Nagasaki bombing.

The declaration followed a pledge made at the Yalta Conference to enter the Pacific War after Germany’s defeat. The Soviet-Japanese Neutrality Pact was still formally in effect, but the Soviet government ended that neutrality and announced war late on August 8. Soviet forces invaded Japanese-held Manchuria just after midnight on August 9.

The United States dropped an atomic bomb on Nagasaki later on August 9. This sequence is important because Japan’s surrender resulted from a rapidly changing strategic crisis rather than a single isolated event. The Hiroshima bombing had occurred on August 6, while the Soviet entry opened a major new front in Northeast Asia.

Emperor Hirohito’s surrender broadcast followed on August 15. The formal surrender document was signed on September 2, after Soviet and Allied forces had begun occupying or accepting Japanese surrenders in several territories.