Wanted to add this little 2003 survey of nuclear first-use policies. It had some info as to how India, and other nuclear weapons possessing countries, came to their official policy of no first-use. It also strongly advocates a no first-use policy for the U.S. that seems, at first glance, to be similar to that adopted in the 2010 Review I cited above.
As to Szlater’s points about Afghanistan, I’ll just point out that the Afghan militants have not used a WMD in the United States (or at all, really.), and that the degree of thwarting would probably change if one had been used. It has been sufficient to prevent Afghanistan from developing a nuclear weapon though, which is all I think **mlees **was trying to point out with respect to Iran.
True, the alleged hardening of Iranian nuclear material enrichment sites might require a nuke to collapse them. A technical problem with doing so—beyond breaching the nuclear taboo—is that such collapse requires a groundburst. Groundbursts produce hideous local fallout that is unlikely to remain with Iranian borders, no matter how “clean” the weapon. (Yes, the bunker-buster that would be used would be a lot smaller than Castle Bravo; still, 1000 rads accumulated over 4 days within 150 miles+ of Ground Zero is one hell of a an irradiated area.) Bushehr, where Iran’s main reactor is located, is on the Persian Gulf, about 175 miles from Kuwait City. Even if you get the wind right, use a clean warhead, you’re still killing hundreds of innocents. Thousands if we count cancer. At best.
Consider this study from Physicians for Social Responsibility. Now, they aren’t LLNL, and they definitely have an ax to grind (among other things, using a 1.2 Mt warhead, when the likely warheads are going to be much smaller), but just look at the projected fallout plumes. A whole lot of ordinary people are going to be irradiated, and they won’t know that they’ll need to take shelter. I cannot see Iran’s neighbors accepting irradiation in exchange for a certain collapse of Iran’s various nuclear production facilities.
More likely, IMHO, is that all of the entrance points to the buried complexes would be bombed, with an unknown likelihood of sealing those points. Perhaps exotic warhead compositions like thermobaric mixtures (Maybe the fuel-air explosive will be dusted off the shelf?) would be used to try and get the explosive material deep within the complex. Worse comes to worst, declare war and drop a Ranger regiment on the damned thing. The point is that there are plenty of choices before breaking out the nukes.
Or, the U.S. will ignore Iranian attempts to produce a bomb, and remind them that use of such a weapon, or negligent loss of same that results in use, comes with grave consequences. I hope that this will be the result. I realize though, that the greater that these weapons proliferate, the greater likelihood that one of their owners will miscalculate and conclude that their existence is threatened. And then they will be used.