The biggest defense against a nuke is to be everywhere, without too many resources in one place.
MAD is obsolete the second the nukes stop firing, and that either happens when the warring countries die or they take the world down with them.
That doesn't really have to do with anything. That is basically the same thing as balance of power in world politics, except with nuclear fire. We certainly haven't had any world wars since nukes were invented, thus so far it seems more stable, no?
Yeah Culise, I've read the post 1945 "pre-emptive war" arguments, and it envisions a world quite unthinkable. In a world where nukes have no taboo, and where only one country has them, all balance of power arguments end. From a foreign-policy perspective, nukes are a perfect dream: no fuss, no soldiers lost, costs insignificant to that of maintaining a real army, no opposition except from pacifists; basically a war solver in a single-use. Inhumane, perhaps, but a real war isn't much better. Imagine if nukes could be used for any purpose, to solve any problem from USSR to Korea: North Vietnam would have yielded in a day, and if it hadn't, you could simply wipe them off the face of the earth; Napalm could kiss Nixon's ass. The US would have unparalleled dominance, over every country in every continent. Any serious war with the US would be outright suicide; better to simply surrender immediately and pray for safety.
Sure, it wouldn't be a cure-all, but in the early 40s the Taliban were nothing but dreams in a distant future, Al Queda unheard of (and possibly never to form, since the US would have simply nuked the USSR away, so no training for militants). Tsuchigimo, I have heard (but not totally confirmed, though I have run some numbers) that the US had, at least at one point, enough nuclear weapons to kill all people on earth: clearly dispersion is no obstacle. In a solely selfish rational POV, the US should have nuked Russia with all the (admittedly few) nukes they had at the time.
This discussion reminds me of a certain someone.