Iran’s Attack on Israel Has Deepened Concerns About Its Nuclear Program

Iran’s decision to launch more than 300 missiles and drones in its first direct attack on Israeli soil earlier this month showed an appetite for risk that is putting renewed focus on Tehran’s nuclear program and whether it will continue to refrain from developing a bomb.

Close observers of Iran’s nuclear development have long believed the country’s top leaders have calculated that the costs of building a bomb outweigh the benefits. As a threshold nuclear power with weapon capabilities within reach, Iran already enjoys considerable deterrence power without risking the war that could come if an attempt to build a bomb is detected.

But that thesis has been shaken this year. As tensions with Israel grew, top Iranian officials have made a string of statements hinting that Tehran is close to mastering the technicalities of building a bomb.

Hours before Israel hit back at Iran, a senior officer in Iran’s Islamic Revolutionary Guard Corps said Tehran could reverse its restraint on building a bomb if Israel struck its nuclear facilities.

Israel’s limited response went after targets around Isfahan, where Iran has nuclear facilities, but didn’t attack those sites directly.

“The escalation between Iran and Israel may strengthen Iranian calls for weaponization,” said Raz Zimmt, senior researcher at the Institute for National Security Studies. “So, while the risks of such a move continue to outweigh the advantages, the Iranian leadership is more likely to reconsider its nuclear approach than previously.”

Israel is widely believed to have nuclear weapons but has a policy of never confirming or denying their existence.

Before this month’s direct strike, Iran had primarily confronted Israel via a network of regional proxies and has used the threat of engaging those militias, particularly Hezbollah in Lebanon, to deter more aggressive action by Israel. The exchange of attacks on each other’s territory has left the foes in a more dangerous competition as the new rules of engagement firm up, analysts say.

Iran’s failure to damage Israeli military sites during this month’s attacks could persuade Tehran to seek a more powerful deterrent. Zimmt says challenges in controlling and operating the proxy network, whose interests don’t always line up with Tehran’s, also could add pressure on Iran to pursue a bomb.

Iranian officials have fueled such thinking with a pattern of references to the country’s near-nuclear capabilities. In an interview broadcast in February, former Iranian Vice President Ali Akbar Salehi, a key figure in Iran’s past nuclear work, said Iran has crossed “all the thresholds of nuclear science and technology,” comments later echoed by the current head of Iran’s atomic agency, Mohammad Eslami.

U.S. intelligence services and international officials have said as recently as March they don’t believe Iran has resumed the nuclear weapons program it is thought to have pursued in the 1990s and 2000s. Yet the country has moved forward on several fronts needed to develop a bomb, including via studies and activities that it says are civilian work.

David Albright, president of the Institute for Science and International Security think tank, said it would take only six months for Iran to build a few basic bombs that could be delivered by truck or ship.

Iran in 2021 resumed work on uranium metal, which is crucial for putting highly enriched uranium into the high-density form needed for a nuclear weapon, and appears to have made progress on the package of high explosives needed to induce a nuclear explosion.

The country’s enrichment program is now significantly more advanced than it was when a deal limiting its nuclear program was reached in 2015. President Donald Trump withdrew from the deal in 2018. Since then, Iran has installed more than 1,000 advanced centrifuges that work faster than its previous equipment at enriching uranium to higher levels of purity.

Tehran has increased its stockpile of 60% enriched uranium—near weapons-grade material that could be further processed in a matter of days to fuel around three nuclear weapons. It also has ended monitoring by the United Nations atomic agency of some of its enrichment infrastructure, like factories for making centrifuge parts, that had previously taken place under the nuclear deal.

That loss of visibility, the International Atomic Energy Agency has said, could make it impossible to know how many centrifuges Iran has, which could help it develop a covert enrichment program.

Keeping an enrichment program hidden would be challenging. With IAEA inspectors permanently in Iran, cameras at its official enrichment facilities and Iran’s nuclear activities under close watch by Western intelligence services, it would require fitting out a secret enrichment site and a hidden conversion facility for producing the gaseous form of uranium that can be enriched.

But IAEA Director-General Rafael Grossi warned last month that the agency’s reduced visibility into Iran’s work means it may not always be able to guarantee that Tehran’s nuclear program remains peaceful.

“I am concerned about the ability of my inspectors to be able to put the jigsaw puzzle together again,” he said.

The consequences of trying to build a bomb could be severe. President Biden has vowed to stop Tehran from producing nuclear weapons. Israeli officials have said they would act militarily to stop Iran building a bomb.

Iran’s development of basic nuclear weapons—or even evidence of a successful underground nuclear test—would likely precipitate an international crisis and complicate a military response.

Iran is developing a network of deep underground tunnels at its Natanz enrichment facility that offer protection from attack. Its other enrichment site, Fordow, is buried deep in a mountain.

Until it can build multiple reliable weapons that could be mounted on midrange ballistic missiles—the original goal of its old nuclear weapons program—Iran would remain exposed militarily. That could require a few years of work, experts say, which Tehran would have to try and keep secret.

Iran continues to advance its ballistic missile program. But Vann Van Diepen, a former U.S. intelligence officer, said Iran didn’t integrate its ballistic missile program into its past nuclear work, leaving crucial testing of how warheads and their components would work on Iranian missiles far from complete.

For example, Iran isn’t believed to have done the vibration and temperature tests needed to be confident a weapon would survive the conditions it would experience during flight and re-entry into the Earth’s atmosphere, Van Diepen said.

Ultimately, the decision to move ahead would be political. The concern is what lessons Iran takes from its recent exchange of fire with Israel.

“Recent events raise the worrying possibility that Iran might conclude its current deterrent is inadequate and that it actually needs nuclear weapons,” said Eric Brewer, a former National Security Council director for counter-proliferation who is now at the Nuclear Threat Initiative, a nonprofit organization. “As far as we know, the Supreme Leader hasn’t decided to build nuclear weapons. That suggests he thinks Iran doesn’t need them or the risks of getting them are too high. We should work to keep it that way.”

Carrie Keller-Lynn contributed to this article.

Write to Laurence Norman at [email protected]