Reasons for dropping atom bombs in 1945

Reasons for dropping atom bombs in 1945.

1. By the time scientists had developed the atom bomb Germany had surrendered, and so it was no longer needed for use in Europe.
2. It was estimated that if the US were to go into a fully-fledged invasion of Japan, over half a million American troops would've died, along with a more drawn out war and further suffering/casualties of Japanese citizens too.
3. The first bomb ("Little Boy") was dropped in an effort to force Japan to surrender, avoiding the high predicted casualties in the hopes of bringing a fast end to the war.
4. After Japan still hadn't surrendered, three days later the second bomb ("Fat Man") was dropped on Nagasaki to show Japan how powerful the US was and further force surrender.
5. The US wanted to use the bomb before the USSR entered the war against Japan to establish American dominance.
6. The US wanted to be the first to use such a weapon and observe the effects.