Japan was on the opposing side of a world war where they were trying to reach global domination with Germany and Italy. And they were succeeding very well. That's why we dropped the nuclear bomb. Not just because of them attacking our harbor - we were trying to prevent a global take over by an evil Empire. It matter's not. America wasn't participating in the war until we were attacked (as far as I've ever been told?), so we attacked back via nukes. It was a bit excessive, really. :P hmm... seems you are quite lacking regarding your own history in the world wars? The US pretty much level most of the Japanese cities during WWII, though they use the more conventional methods before the Bombs came into play. I think that the US had some sanctions against Japan before Perl Harbour denying them some vital resources for their war efforts, though if that's what provoked them into attacking I do really know. And the US was island hopping in the pacific for quite a few years before they nuke Japan. Now for the actual subject matter... The UN is just like a Forum for the world governments and only has as much power as its member states are willing to give it, and its pretty much usless unless the security council comes to an agreement, which is not very often against issues like these when everyone has their own interest to look after.