In August of 1945, the final days of the war, the Soviets rolled a fearsome ground army into Japanese-controlled Manchuria to push the outlying forces back. This was part of a joint Allied strategy and actually began the same day as the United States dropped an atomic bomb on Nagasaki, because this strategy was apparently codenamed Japan Can Go Straight to Hell. Japan was thoroughly crushed by the combined offensive (we daresay probably more so by the two doomsday explosions leveled at them with weapons that no one had ever seen before) and surrendered six days later, signing the official surrender documents in early September.
However, according to some historians, the USSR originally had no intention of stopping at Manchuria. It was supposed to be the pre-game show of a full-scale invasion of Japan itself, which would've seen the Red Army folk-dance its way across the Pacific Ocean and squat-kick the island nation into submission.
It would have looked exactly like this.
The Soviets planned to begin their invasion in the northern Japanese island of Hokkaido in late August, a full two months before the Allied invasion, Operation Olympic, was scheduled to take place. However, Stalin kept his plan a secret from the other Allied forces and had absolutely no intention of telling them anything about it, preferring to wait until the forces of Operation Olympic stormed the shores of Japan to find him sitting in the emperor's palace watching cartoons. In fact, some theorize that Japan surrendered not because they were afraid of more atomic bombs from the U.S., but because they were afraid of the Soviets.