Targeted strikes against the sites affiliated with Iran’s nuclear fuel cycle would certainly set back for a number of years Iran’s heavy-water reactor construction project at Arak and its ability to convert large amounts of uranium ore to uranium hexafluoride at Isfahan. They would also likely destroy Iran’s centrifuge plant at Natanz, notwithstanding its hardening against such attacks.
[But] destroying the facilities without the equipment and materials would not set back the enrichment part of the program significantly. Moreover, rather than possibly delaying or making it impossible for Tehran to carry out a final decision to make nuclear weapons, an attack might force the Iranian leadership’s hand. Iran would almost certainly kick out IAEA inspectors and, freed of any international restraints, might well accelerate any weaponization efforts, launching a Manhattan Project-style undertaking in defense of the homeland. In such a case, the United States would likely be forced to launch and sustain a long, costly war against Iran.
In the case that the United States launched a broader attack, causing far more destruction of Iranian infrastructure and disruption of the leadership’s ability to retaliate, the United States would be faced with the same problem. There would simply be no assurance that Iran’s ability to make nuclear explosive material would be significantly curtailed as long as it possessed covert facilities or the means to build and operate them. Finding them would be like looking for a needle in a haystack.
This report by former weapons inspector David Albright and Jacqueline Shire for the Arms Control Association details at length what we think we know about the Iran nuclear weapons program (and its a good primer for anyone who wants to bring themselves up to speed on the issue) but it concludes with a section on why an attack on Iran cannot destroy their nuclear weapons capability, which I've excerpted above. An extensive air offensive against targets in Iran will do much to degrade their ability (and knowing the Bush administration, such an offensive will probably also include strikes against other non-nuclear military targets.) But it will not destroy it. And the ground offensive that would be necessary to substantially eliminate the possibility that a program survived the air offensive, is impossible and off the table, even for this administration.
So the war hawks, for whom the solution to a bad war has always been another war, make many critical assumptions. They assume that if we strike Iran, we can get all or most of their nuclear program. They assume an attack can forever forestall Iran's ability to get nukes. They assume that the Iranians cannot punish us in turn for just such an attack. And they either assume that the bad consequences that will follow from an attack would not be truly harmful for us, or that those consequences are less harmful than the consquences of letting Iran have nukes.
They're wrong about all of them. A military strike won't work, and it will be far more harmful to us than letting Iran have nukes could ever be. The American people seem to agree, though of course the opinion of the people has hardly counted for much to this administration.