A military strike will delay but cannot stop Iran from acquiring nuclear weapons. It will increase support for the Iranian government at home and abroad. And it will cause catastrophic damage in a global economy barely past the worst financial crash since the Great Depression.
Sanctions and diplomacy promise little more. The Russians and Chinese refuse to stop supporting Tehran, and the Iranian government simply isn't interested in negotiating.
That leaves containing Iran, whether it has nuclear weapons or not. Containment denies external success to Iran through measures such as isolation, trade and financial embargoes, noncommunication, and nuclear deterrence.
One goal is to force the regime to abandon its dream of international dominance and, ultimately, to accept regime change at home. Critics object that this will take too long and argue that, in the process, Iran will acquire nuclear weapons. A nuclear Iran, they say, will then enjoy greater freedom of action in the region because of a mutual fear of nuclear escalation.
But that mutual fear can work both ways – as it did for decades in the cold war with the Soviet Union. The greatest danger of a nuclear Iran – that it will use its weapons, presumably against Israel – can be negated through Iran's sure expectation of a catastrophic nuclear response from either Israel or the United States. Beyond deterrence and isolation, though, the US and its allies must foster a world outside embargoed Iran that is so dynamic, prosperous, and attractive that Tehran will be unable to take advantage of any psychological or political leverage it gains by going nuclear.
Protected by an American nuclear umbrella, friendly governments in the region can focus on economic and social development. That will give them the strength to resist Iran's leverage.
Edward Haley is W.M. Keck Foundation professor of international strategic studies and director of the Center for Human Rights Leadership at Claremont McKenna College.