Originally Posted by pocketkangaroo

Japan tried to kill American civilians (and did) as well. If they could have reached the US, they would have dropped a bomb on us.

It was a military decision, and the invasion of Japan would have caused more civilian deaths and US military deaths. The fact is put a quick end to the war was a huge factor, as both sides were racking up large civilian deaths (look up Japan's scorched earth policy). Japan was being blockaded, which meant many people were starving. They were also holding other countries hostage and using their citizens as slave labor.

The bombs cost a lot of lives, but it was a decision that may have prevented many more in the long run.