Two days after the U.S. dropped its first atomic bomb on Hiroshima, the Soviet Union declared war on Japan.
The Soviets — under Joseph Stalin — had earlier promised a formal war declaration against Japan three months after the defeat of Nazi Germany, but the timing fed growing concerns that the Soviets were positioning themselves for Communist expansion in Asia — most notably the Korean Peninsula. Korea had been under Japanese control for decades, and with Japan’s surrender imminent, the question was, who would exercise post-war control over the Korean Peninsula. The stated intent was to ultimately see Korea as an independent, self-governing country.
That was not to be.
Within days, Soviet troops crossed from Manchuria into Korea.