If a Nuke is dropped, what will happen next?

I imagine that whoever drops it first will have brought a savage war upon us. Not just a war but a nuclear war. And the real worrying thing is then who is involved, how does North korea feel about America imposing a nuclear strike on Iran. How does China feel.. how bout Russia.
Trade relations won't be the same and it'll only take ONE of these nuclear super powers.. to retaliate to what America has done and give em a taste of there own medicine.

So.. the big picture I'm looking at is.... A NUCLEAR WORLD WAR!
It will take all the idiots in power, and theres alot of em to do what the do best and screw the world up even more..

To me the biggest threats for a N.W.W are America, Iran, North Korea, China and Russia.