Two months ago, General Mark Welsh, the U.S. Air Force chief of staff, revealed that the 509th Bomb Wing’s B-2 bombers were now equipped to carry new 15-ton bunker-buster bombs developed with an eye on Iran’s nuclear facilities.
If negotiations in Vienna to curb Iran’s nuclear program fail, however, even an airstrike with the 30,000-pound Massive Ordnance Penetrator -- the largest non-nuclear bomb ever developed -- would delay Iran’s nuclear efforts by only a few years, according to U.S. defense officials and private analysts. Israeli forces could do far less, these experts say.
The prospect of an attack on Iran hovers over debate about what the U.S. should do if a solid agreement to curb Iran’s nuclear program can’t be reached. President Barack Obama has frequently said he hasn’t ruled out any options, and Republican Senator Tom Cotton, an administration critic, has said military action against Iran would take only days.
That’s not what the American intelligence community has concluded, according to Senator Angus King, an independent from Maine who sits on the Senate Armed Services and intelligence committees. U.S. strikes might set Iran’s “program back two-to-four years, but it can’t destroy it,” King said in an interview.
“You can’t bomb knowledge out of them,” and probably “all doubt would be erased” that Iran would respond by pursuing a nuclear weapons program, he said.
Defense Secretary Ashton Carter said Wednesday that while a military strike would cause a “setback” for any Iranian nuclear-weapons efforts, “it doesn’t prevent the reconstitution over time.”
So in planning for such a situation, the Pentagon has anticipated the possibility of an open-ended military operation against Iran if necessary to prevent nuclear-weapons development.
“The military option isn’t used once and set aside,” Army General Martin Dempsey, chairman of the Joint Chiefs of Staff, said at a Pentagon news briefing. “It remains in place, so we will always have options and the massive ordnance penetrator is just one of them.”
A single military strike “would only delay an Iranian drive” for “a finite period” so a credible “military option would have to envision a long-term campaign of repeated follow-up strikes as facilities are rebuilt or new targets identified,” Kenneth Katzman, Middle East analyst for the Congressional Research Service, said in an e-mail.
“This is within the U.S. capability, but would require policy consistency and sustained determination across several U.S. administrations,” he said. “What is crucial” is not the bomb, but a “multiyear campaign of vigilance” and “precise intelligence of new targets,” Katzman said.
The exact dimensions of Iran’s nuclear infrastructure aren’t public. Among potential targets would be a fuel enrichment complex at Natanz, a heavy water production plant and heavy water reactor near Arak, and a uranium conversion facility and three small research reactors east of Esfahan, according to a roster of Iranian nuclear facilities developed by the nonpartisan Institute for Science and International Security in Washington.
The toughest target, U.S. military and intelligence officials have said, is the Fordow site, buried deep beneath a mountain about 20 miles (32 kilometers) from the holy city of Qum. Obama revealed the existence of the previously secret nuclear enrichment facility in September 2009.
Starting that year, Defense Secretary Robert Gates and Admiral Michael Mullen, who was chairman of the Joint Chiefs, said strikes might delay Iran’s program by as long as three years.
But Gates cautioned in April 2009 that air strikes “will only buy us time and send the program deeper and more covert.” Bombing “would also bring together a divided nation and make them absolutely committed to obtaining nuclear weapons.”
“You’ve got to be careful of unintended consequences here,” Defense Secretary Leon Panetta told reporters in November 2011, the same month the U.S. took delivery of its first MOPs, which were modified in 2013 to attack more deeply buried targets.
“Those consequences could involve not only not really deterring Iran from what they want to do, but more importantly, it could have a serious impact in the region and it could have a serious impact on U.S. forces” there, Panetta said.
Still, the largely unspoken subtext for media reports touting the GBU-57 Massive Ordnance Penetrator, or MOP, is that the U.S. has the military capability to destroy the nuclear program, if necessary.
Carter, referring to the bomb known as a bunker-buster, said on CNN that, “we have the capability to shut down, set back and destroy the Iranian nuclear program. And I believe the Iranians know that and understand that.”
Republican Cotton of Arkansas, who’s skeptical that the administration will reach a deal effectively curbing Iran’s nuclear program, said in a separate interview, “If the question is, ‘Can we eliminate or at least significantly set back Iran’s nuclear weapons program?’ The answer is it is possible.”
Michael Eisenstadt, a military analyst with the Washington Institute for Near East Policy, said the bunker-buster, along with other capabilities, gives the U.S. a credible military option, “though I don’t believe that the Obama administration would use it.”
“But the question is, what would its long-term impact on Iran’s nuclear ambitions be?” Eisenstadt said. Iran says its nuclear program is solely for civilian purposes.
The Iran Project, a bipartisan group of former national-security officials and foreign-policy specialists, said in September 2012 that a U.S. or Israeli attack would derail the suspected weapons program for four years at most, while uniting Iran’s citizens and alienating the Muslim world.
“Complete destruction of Iran’s nuclear program is unlikely, and Iran would still retain the scientific capacity and experience to start its nuclear program again,” the group said. That’s even if B-2 bomber missions were “carried out to near perfection,” it said.
In May 2013, retired Marine Corps General James Cartwright and former chief of Israeli defense intelligence Amos Yadlin reiterated the limits to U.S. military action in a policy note for the Washington Institute.
“Mechanically damaging the program is not an end in itself since no amount of bombs can destroy Iran’s nuclear know-how,” they wrote. Cartwright, who retired in August 2011 as vice chairman of the Joint Chiefs, was involved in contingency planning against Iran.
“It’s hard for me to imagine that” after a U.S. attack “there would not be hundreds of centrifuges left intact, or at least that hundreds could be assembled from the parts that remained salvageable,” Greg Thielmann, senior fellow at the Washington-based Arms Control Association and a former State Department intelligence official, said in an e-mail
“With no inspectors on the ground and a united Iran establishing nuclear weapons as a very high priority, I would think it could recover its position in three to four years, no matter how impressive the U.S. air campaign.” Thielmann said.