What follows is my understanding of the North Korean nuclear standoff, based on my admittedly limited information sources and understanding. This opinion should by no means be considered gospel; it’s just what it looks like from where I sit, for what it’s worth.
North Korea wants to be taken seriously, so they’re acting like a bully on the school grounds talking tough.
They have some nukes; nobody knows how many, or whether they can be fitted to the missiles they are playing with. Most likely, if they can currently mount one on a missile at all, there are only a few. Of course, it’s not the sort of thing you want to be wrong about. The threat is a real one, because Kim Jong-il is a fruitcake, and he’s got total authority to launch. So, he’s got a lot of capability to kill a bunch of people, if the whim takes him.
He should remember one thing, though. He has a few nukes, and can cause a lot of destruction and death, with a preemptive launch; but there are quite a few countries, the United States included, that have the nuclear firepower to literally pave North Korea with radioactive green glass.
The real question is whether Kim Jong-il cares about this.
The reason Mutual Assured Destruction (MAD) worked in the cold war is that both the U.S. and Russia (and others) recognized that none of the parties who had the capability wanted to destroy the human race in a silly nuclear war. Safeguards in these countries were put in place such that no single nut-case could launch the nukes (we hope). Countries run by all-powerful dictators (or religious zealots such as in Iran) may not have such safeguards.
The logic of MAD may not have any bearing on Kim Jong-il (or Iran). We’ll see.
If this seems a little unreal to you, try looking up the stories of the survivors of Hiroshima and Nagasaki. Fascinating, and frightening reading; the format is lousy, but the story is important. And the atomic bombs involved were much less powerful than the hydrogen bombs that are now deployed.