The biggest question about the end of World War II, and is still debated today is, "Should Truman have used the Atomic Bomb?"
The Atomic Bomb was, and still is, the most destructive force ever developed. It is also the most indiscriminate weapon ever known. When the Atomic Bombs were dropped on Hiroshima and Nagasaki they killed Men, Women, and Children. They killed Combatants and Non-Combatants. People who worked in war related industries, and those who didn't. And the bomb didn't stop killing when the explosion dissipated, radiation that was barely understood continued to kill for decades, and may still be shortening lives today.
There are justifications: Not using the bomb would have meant an invasion costing casualties equal to or greater than the toll of the Bomb. Not using the bomb would have required Soviet assistance, and thus Japan would have become divided like Korea and Germany.
There are also counter-arguments: the invasion would only have killed combatants, Soviet involvement wasn't necessarily a bad thing.
There are also unanswered questions: Couldn't we have demonstrated on a desert island? Weren't there other alternatives?
These questions linger today, people debate them still and cannot come to an answer. These questions are also brought up about the possibility of such weapons ever being used again. If Truman was justified, why was he? If he was not justified, why not?