IT’S THE DETERRENCE, STUPID: Iran: The President says this is the best deal available. He’s right; it’s the best deal he could get—absent a credible threat to use force.

If military capacity were all that mattered, Iran would never have dared to build the full-scale uranium enrichment capacity that it now possesses. Intentions matter as well, however, and here the Iranian leaders have calculated—correctly—that the American government would not use its military trump card to halt Iran’s progress toward nuclear weapons. As President, Barack Obama repeatedly asserted that, where that program was concerned “all options”—including, by inference, the use of force—were on the table, but the mullahs rightly surmised that this was a bluff and, by continuing to build the enrichment program that Obama had vowed not to tolerate, they called it. This is the sense in which the Obama Administration’s description of the deal as the best one available is correct. Given that it was negotiating from a position of self-imposed weakness, it is difficult to see how it could have obtained more favorable terms than the ones embedded in the July 14 agreement. . . .

All of this is to say that, at this very late date, keeping Iran from acquiring nuclear weapons, with all the catastrophic consequences that that would have, depends on a credible threat to use American military force. This is true even in the highly unlikely event that the process of inspections works as the Obama Administration claims it will. For if and when inspections in these circumstances detect violations, or the Iranian regime simply decides to withdraw from the agreement, as its thirty-sixth paragraph permits, what will the United States do? Nuclear nonproliferation in the Middle East ultimately depends, that is, not on the details of the Vienna agreement but on the familiar Cold-War policy of deterrence.

Even under Bush, it seemed as if the Iranians had more leverage than was visible. I can speculate on where that leverage came from, but that’s all it would be.