In late May, at a major security conference in Tel Aviv, former Obama Pentagon official Michelle Flournoy assured her mostly Israeli audience that a military strike against Iran was very much on the table. But she hastened to add that “any military strike in its most wildly successful incarnation” would set back Iran’s nuclear weapons program only one to three years.That one-to-three year caveat has become more than an estimate. Over the past several years, as Defense Sec. Leon Panetta, his predecessor Robert Gates, former Chairman of the Joint Chief of Staff Adm. Mike Mullen, and other officials have recited it at press conferences and think tanks, it has become received wisdom.But is it true? It’s hard to believe that the United States lacks the military might to destroy the Islamic Republic’s nuclear program—if not in one campaign, then in a series of campaigns to ensure that it doesn’t get the bomb.“I always felt the time frame was very conservative,” (Ret.) Gen. Jack Keane, former vice chief of staff of the United States Army, said. “My judgment tells me that if we did something as devastating as we could do, taking down their major sites, which also means their engineers and scientists, I think the setback would be greater than five years. I don’t like to read too much into people’s motivations, but at times when we don’t want to do something, we build a case in terms of our interpretation that it is too hard or it isn’t worth the payoff.”Indeed, the assessment that Iran’s program could only be delayed began with the George W. Bush White House, as former CIA chief Gen. Michael Hayden recently explained. It’s hard not to conclude that the assessment was driven by political calculations: Because Bush could not embark on a third theater of conflict in the Middle East, it was convenient to say a military strike would not make much difference.In contrast, the Obama Administration has pulled out of Iraq and will soon pull out of Afghanistan. Yet the White House continues to repeat the trope that the program can, at best, be delayed a few years. Just as politics informed the Bush White House’s insistence on the delay-not-destroy mantra, politics of a different sort are informing this White House: This administration is conducting a public diplomacy campaign with the purpose of undermining the capability of a U.S. attack because the administration has no intention of striking.“It’s not unknown for folks in the military to inflate difficulties in order to not do it,” a former Pentagon official told me. “The assessment may reflect the idea that the military has not much appetite to be involved in the Middle East if they don’t have to. In reality, no one knows how long a military strike could set back the Iranians.”Part of the assessment describing only a one-to-three-year delay, the official explained, is based on the fact that nuclear facilities are spread out across Iran and buried deeper than those at the Osirak reactor in Iraq and al-Kibar in Syria, both of which the Israelis successfully destroyed in one day. A strike against Iran might last a month. Then there’s the notion that you can’t bomb the scientific know-how that produced the program. And yet, the former official noted, citing the campaign of assassinations against Iranian nuclear scientists, “you can kill an awful lot of it.”Christopher Ford, a former State Department official who worked on nuclear proliferation issues, told me that the evidence on which the standard assessment is based could have various loopholes. “There are so many assumptions built into the idea that it’s only one to three years,” said Ford. “For instance, it’s true to a degree that you can’t really get rid of the knowledge, but the nuclear-weapons scientists themselves aren’t the only link in chain. There’s other human capital that might be part of your destruction package, like some minor metallurgy specialists, who maybe aren’t working on the most sophisticated parts of the nuclear program, but without it they can’t have one.”Obama officials aren’t telegraphing any of this. Instead, top intelligence and military officials, like Director of National Intelligence James Clapper and Adm. Mullen, keep saying that the Iranians can be only minimally delayed. Keane, the retired four-star general, believes that’s because the White House, as much as it claims it won’t allow Iran to get a bomb, isn’t willing to strike. “I don’t believe this administration has any intention, ever, of attacking Iran,” says Keane. “I don’t believe it, the Israelis don’t believe it, and the Iranians don’t believe it.”But Uzi Arad, Israeli Prime Minister Benjamin Netanyahu’s former national security adviser, strongly disagrees. “I don’t belong to the camp of skeptics who have little faith in the president taking action if necessary,” he said. “I think the president has recognized, for reasons that have to do with U.S. national security, economic interests, and his conviction regarding proliferation, that if all other measures fail to stop Iran from going nuclear he has to take coercive action.”Arad said he sees no contradiction in the Obama administration’s stated policy (Iran can’t get a bomb) and its caveats (an attack will only delay the nuclear program). “The declared objective, as the president has termed it, is that the U.S. is determined to prevent Iran from developing or acquiring nuclear weapons,” said Arad. “It is inconceivable that the American military would say ‘we can strike but we cannot accomplish our objective.’ The assessment of one to three years assumes one blow but that is not what the reasonable American option is, which calls for repeated attacks if the Iranians restart the program. It is unreasonable to assume that after the strikes the U.S. would sit pat and Iran would rebuild. It’s absolutely imperative that if the U.S. strikes, its posture should be, ‘Dear Iranians, please do not proceed to rebuild the program, or we will strike again.’”Ford, the former State Department official, pointed to a number of variables that might affect Iran’s ability to reconstitute its nuclear program in the event of an American strike. “If you’re just talking about the various nuclear facilities and bombing those things once, then it’s a pretty straightforward calculation: How long would it take to rebuild those things? But those estimates would change under a number of different circumstances. For instance, would you keep sanctions on Iran after attacking? Then it’s a different calculation.” He sees Iran’s air defenses as a key variable. “If you go after the nuclear program you need to go after how they defend themselves. If you succeed in degrading their defenses, it’s not the sort of thing that can be immediately repaired, and Iran has to choose whether they would prioritize reconstituting their nuclear program or rebuilding their air defenses. And if you’ve destroyed a lot of their potential delivery system and missile-production infrastructure, they might want to rebuild that too, which might be more expensive than replacing the nuclear weapons effort itself.”Most important, Ford added, “there is the question of whether you’re willing and able to go back. That is, to hit reconstitution efforts on an ongoing basis. If it’s not a ‘snapshot’ hit but a campaign—that can change the reconstitution equation too.”Perhaps so, but long before the United States decides to attack Iran, we need to communicate our seriousness to the regime. “There is only one guy you need to convince here to voluntarily give up the nuclear program and that is the Supreme Leader Khameini,” Jack Keane argues. “He must know we are dead serious about a military strike, as a last resort, and this is not just about the nuclear facilities—their military will be decapitated. This is the U.S. military. Believe me, we will destroy you.”***\nLike this article? Sign up for our Daily Digest to get Tablet Magazine’s new content in your inbox each morning.Lee Smith is the author of The Consequences of Syria.