It also saved us from having to fight in Japan TWICE.
Had we not dropped the bombs, the Soviets would have gotten into the fight and demanded their half of Japan. So we would have had a divided Japan, just like Korea. And the resulting civil war would have made Korea look like a walk in the park.
Interesting point!
The reason why Roosevelt was so compiant with Stalin at Tehran and Yalta was his conviction that he needed Soviet help to defeat Japan, and their agreement for his real dream, the UN.