I just want to note in regard to Andy’s post that examining the constraints on a possible military attack on Iran does not assume that such an attack is desirable in purely strategic terms. I would sum up the issues as such:
a) A nuclear-armed Iran is likely to be very destabilizing. While Andy seems quite comfortable with the idea that such an outcome is no big deal because of the impact of deterrence, I’m not convinced. First, the issue is not whether “Iran” as a decision-making totality is rational. It may be that Iran will not have the same command and control structure that the Soviet Union had, and thus senior decision-makers may not be able to impose their rationality (such as it is) on their possible use. Second, Iran may not have the same scruples of allowing nuclear weapon technology to leak out to non-state actors. Third, deterrence works two ways–Iran may be limited in the ways that Andy suggests in actually using a nuclear weapon, but its possession may give it leverage in, for example, developing other weapons or pursuing larger strategic objectives. Finally, “rationality” may have a somewhat different meaning with a leadership structure that possesses the beliefs that the Iranian leadership did.
b) All that being said, it is quite difficult to imagine any actions the US could take of a directly military nature that would not have highly unpredictable outcomes. We can spin these out as far as we’d like, but the point here is the very uncertainty of the blowback, which makes calculating the cost-benefit structure here difficult, if not impossible. In addition, as Andy rightly notes, the civilian casualties may be extremely high, which has to be weighed seriously against the factors in (a).
c) On the other hand, the relevant actors here are not just the US, Europe, and Arab states of the Middle East. If those actors do not restrain Iran’s nuclear ambitions, it is difficult to imagine Israel failing to do so–it is not unreasonable that Israel would see a nuclear-armed Iran as an existential threat. As destabilizing as a major war between the US and Iran is, a war between Israel and Iran is worse. So even if we concluded that, on balance, (b) outweighed (a), (c) could effectively settle the matter.