Odds are, without the bombs, at least half of Japan would have been occupied by the Soviets, and a Korea-like Civil War would have been inevitable, and we would have been involved in it.
Odds are, without the bombs, at least half of Japan would have been occupied by the Soviets
Yep: at least in terms of the timing, the A-bombs were about the Soviets as much as the cost of a potential invasion of Japan itself.
At Yalta, FDR gave away the Kuril islands to the Soviets, but they also wanted Kokkaido, the northernmost mainland Japanese island. A week after the Nagasaki bombing Truman had to reassert that no Japanese main islands would be taken by the Soviets, who had invaded Manchuria on August 9 (mere hours before the Nagasaki bomb). It is certain that without the A-bombs forcing the Japanese surrender to MacArthur, the Soviets would definitely have invaded Kokkaido.
On July 24 at Potsdam, Truman confirmed to Stalin that we had the bomb ready. The next day, Truman signed the order to drop the bombs, with a go-date of August 3. Soviet positions above Manchuria were already in place and ready by early August, and we not only knew it but helped the Soviets prepare it. But the Soviet plan was for an August 15 declaration of war and invasion. However, the Hiroshima bomb caught them by surprise, and Stalin launched the attack right away.
The timing of the Nagasaki bomb was dictated by logistics and weather, not by the Soviet declaration. The Japanese surrender definitely was in response to both.