I dont think meaningful sanctions make any kind of sense. North Korea is already a fairly unstable state, now theyre unstable with nuclear weapons. It won't help anyone in range to further destabilize the country.
The fact is nuclear proliferation is here. The technology is out there now and its not as hard as it used to be to figure it out now that the major powers have done all the heavy lifting. Unfortunately, you don't have to be a major power to put a nuke on the table any more.
It makes sense to talk a good game and threaten all sorts of damnation to discourage countries from doing the research and building the bombs, but it's really just to delay the inevitable (a worthy goal in the case of nuclear proliferation. )
Not that the US has done a good job persuading countries that they dont need nuclear weapons lately. The US position has been something like this since Bush has been in office: "we have the bomb, we think youre a threat, so we dont want you to have it too...by the way we think youre evil and are considering invading your country, we'd like to show you some 'shock and awe'"
As crazy as [SIZE=-1]Kim Jong-il is, it was probably the sanest move he could have made to detonate a weapon. If I was running a country that was put on the "axis of evil" by the #1 superpower in the world, then I saw that superpower start picking off countries on that list, I'd probably do it. Its a pretty strong invasion deterrent.
So what happens now? I would guess more countries, particularly ones that have issues with either the US or Russia, will go after the bomb. There will be blustering, but they'll eventually get a weapon. As more inherently unstable countries get the weapon, the chance for a pretty horrible accident goes up. (Here are the
top 20 near-world-ending mistakes between the US and the USSR. If we have this many how many do you think NK, India, Pakistan, Israel, and Iran will have? Yuck) It makes the strategic case for getting back more strongly into missile defense, especially since none of these countries would be launching a fleet of missiles.. a capability to shoot down a handful of incoming ICBMs is likely to pay off for us in the next 50 years. More complete radiation detection at our borders would probably be a good thing too.
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