I actually just watched a documentary NOT on the war itself but on the scientists involved in creating the bombs.
Suprised no one has mentioned this but there were scientists on both sides of the war working for this nuclear weapon. IMO it was not a case of trying to just end the war to try a new weapon. They were intact ahead of the united states by 2 years (if i remmeber right) on making a nuclear bomb and we had no idea how much they accomplished. The united states were trying to find the main scientist leading the research and an agent tracked him down and felt that they were not close enough to launching and chose not to take his life. Later there was an explosion at the main research lab when trying to multiply the nucleus after they split it.
This is what supposidly made the US rush to dropping the bomb. The US thought they already been right at completion. At the end of the documentary the scientist was not charged with any war crimes and claimed he purposely created the explosion to hinder them from launching a nuke first. However, the scientists involved on the united states side were devistated by the amount of damage that was caused and felt tremendously at fault afterwards. (supposedly anyways).
There was so much more to the story but those were main points. Pretty in depth stuff in documentaries. I watched another on of the space exploration. The united states was actually getting shown up for long time and if there leading rocket scientist had not died we may very well have not been first on the moon. (sorry off topic)
Edit - as for obama apologizing... How could he apolgize. If history shows the united states was attacked and we began to retaliate. That would be fine. So if we are then at war and the oposing side is trying to rush developement for a nuke and we know about it then our only way to win was to drop one first... There would be crazy pressure at that time to actually sau yes to dropping that bomb. I can safely say its good thing it was done. Now that it is history and it is fact they would have dropped it first if they could have then why is an apology necessary. Those people who died is tragic but it was from their own countries doing. What else did tey expect when they were trying to drop one first.