The United States is the only country in the world with the ability to destroy the Fordow nuclear facility quickly from the air, something we could accomplish by dropping a couple 15-ton Massive Ordnance Penetrator bombs on the most important and heavily protected piece of Iran’s nuclear infrastructure. Such a strike would potentially reset the entirety of international arms control.

Since the early 1970s, the world has depended on the Nuclear Non-Proliferation Treaty (NPT) regime, the International Atomic Energy Agency (IAEA), and the U.N. Security Council to maintain a global system that regulates the spread and development of nuclear weapons technology, placing American adversaries like China and Russia at the apex of the arms control system and creating layers of bureaucracy and diplomacy that would-be proliferators have learned to exploit. Pakistan, India, and North Korea have all built nuclear arsenals in defiance of the NPT. Until this week, Iran was very close to joining them.

The global arms control regime never considered Fordow—or, for that matter, Yongbyon, the site of North Korea’s nuclear breakthroughs in the mid-’90s—to be sufficiently serious a threat to global peace to warrant military action. Interestingly enough, the three most recent instances of a country using force to stop an in-progress nuclear program—namely, the Israeli attacks on Iraq, Syria, and Iran—were launched by a state that isn’t a signatory to the NPT. So far the United States has declined to attack North Korean and Iranian nuclear sites. If Donald Trump were to reverse course and bomb Fordow, he would reorient all of global nonproliferation around American strategic judgment and leadership. A successful U.S. attack on Fordow would establish a precedent that a would-be atomic scofflaw couldn’t ignore, with Washington acting as the final bulwark against the spread of nuclear weapons in cases where the NPT regime failed.

But what if Trump decides stanching the tide of nuclear weapons is a job better left to the Chinas and Russias of the world? What if the Israelis are really on their own here? One of the big unknowns of Operation Rising Lion is the extent of the damage Israel has been able to inflict on the Iranian nuclear program so far. Clarifying the issue requires both scientific expertise and deep knowledge of the entire Iranian nuclear-industrial complex.

Almost no one on earth is more qualified to talk about Israel’s progress against the Iranian bomb than the physicist and former IAEA inspector David Albright, founder and president of the Institute for Science and International Security (ISIS). The institute has already published a detailed summary of the likely impact of Israeli strikes on Iranian nuclear facilities. I spoke to Albright on Monday afternoon to get an update on where things stand. The conversation has been edited for length and clarity.

Let’s say, hypothetically, that Israel stopped bombing Iran right now. How far back have they set the nuclear program? Do we even know?

I think it’s been set back significantly, but it’s hard for me to quantify that. The elephant in the tent is Fordow, where if Iran continues to operate, they can break out and make weapon-grade uranium very quickly. I think on the weaponization side, the time to make the bomb has probably been extended by several months.

I think it would be very dangerous for Israel to stop right now. Iran has a big program. There are a lot of parts to it, and it just takes a significant amount of time to really set it back sufficiently to feel like the job is done. Now, if Iran agrees to negotiations and says, we’ll dismantle our program and we’ll come clean with the IAEA then that’s another way to establish the endpoint you want. But if it’s just Israel walking away and then Iran leaves the NPT or just refuses to cooperate with the inspectors, we’re in a worse situation because Iran would certainly be incentivized to move toward the bomb.

It would still be very hard for Iran to move to build a bomb right now. In the long run Iran can replace the nuclear scientists killed this week, but in the short run they can’t. It’s a real shock to the system that makes the nuclear weapon itself.

You also have this destruction at the Isfahan enriched uranium metal production line. So you have just a chunk taken out of the line of things that have to be done to make the weapon-grade uranium core component … I think that Israel is deliberately trying to increase the time frame, I would say by at least a half a year or more, for Iran to be able to make even a non-missile-deliverable nuclear weapon, while also making Iran more scared to start that process.

On the fissile material, it really all hinges on Fordow and how many more centrifuges Iran has made that it hasn’t deployed.

On Friday Israel destroyed the power station supplying the Natanz nuclear facility. I’ve read, including in the ISIS report, that if the centrifuges inside Natanz are left without power long enough they will become permanently disabled. How does that work?

A centrifuge has a rotor that spins at a very high speed. If you cut off electricity, it’ll spin more slowly and finally stop. But as it traverses down from around 450 meters per second, sort of the speed of a bullet fired from a handgun, it’ll hit resonances and will start to shake violently. And then it’ll hit the wall and break. A centrifuge operator has to have a strategy to get through the resonances … but in an uncontrolled shutdown, gradually speed goes down through the resonances and that maximizes the chance of a vibration that leads to the rotor crashing against the wall of the centrifuge’s outer case.

During one of the first deals with Iran, in 2003, Iran agreed to shut down 164 centrifuges, its first cascade. But they weren’t that experienced. One-third broke when they shut them down, and that was a controlled shutdown.

When I read that Israel had destroyed the power source for Natanz without necessarily destroying the underground centrifuge halls, the next obvious question in my mind was: Could something similar be done at Fordow? Is it possible to disable Fordow by attacking the power supply and thus avoiding the issue of having to bomb so deep underground?

They could do that. I’m actually wondering why they haven’t yet. Fordow is much more deeply buried than Natanz. It’s 80 meters or so underground. Israel could take out the ventilation system at Fordow and make it impossible to really work in that environment. I don’t understand why they haven’t yet. They could make it inoperative and if Iran moves to fix it, they can bomb it again. So as long as Israel is active over the skies of Iran, they can keep Fordow and Natanz inoperable.

Can Israel destroy Fordow without American help?

Yeah, I think so. They could mine it during a commando raid. They could potentially crack the ceiling or undermine the support structure of the halls. They can make it very difficult to get into. Effectively that’s destroying it, if you can’t get in without months and months of work. Then when you get in, it’s more than likely most of the centrifuges are going to be broken.

So Fordow’s power supply is above ground?

Yeah. There are no generators underground as far as I know.

What do you make of Israel’s strategy with Fordow so far? It was reported yesterday that there was a small earthquake in Fordow, and there’s been video online of columns of smoke coming from the area of the facility, but it doesn’t seem as if Israel’s made it the primary target of what they’re doing so far.

I can only speculate. I mean, it’s possible they’re trying to leverage the United States to destroy it because the U.S. could drop a couple of bunker-busters and the ceiling and the main halls would collapse and it’s the end of the story. Iran could never rebuild it. The rock would be too unstable. They’d have to go someplace else and start anew.

It’s possible the Israelis aren’t that worried about Fordow and have some information that says, no, Iran’s not making weapon-grade uranium at Fordow, and it’s on a list, and they’ll eventually get to [attacking it]. But it is a mystery to me.

Can Israel disable Fordow without destroying it, and without the use of large bunker-busters?

They could take out the electricity. They could destroy the ventilation system. They can easily destroy the pedestrian entrance. They can destroy the main entrances. There’s two, and they can even use more powerful armaments to work their way back to the tunnel entrances. They can’t get to the [centrifuge] hall perhaps, but they can get a good way there. It would be inaccessible for months. And then they can always go back if there’s some sign of the Iranians trying to dig out new tunnel entrances, but I think it would be tough for them.

Israel destroyed an advanced centrifuge manufacturing facility in Iran in 2020. After that Iran said, okay, now we’re going to put that underground, under this mountain near Natanz, and it’ll be done in a year or two. It’s now been four or five years and it’s still not done. So it does take them a long time to recover from these kinds of actions. I think Fordow could be kept inoperable for quite a while. And then you can go back. It’s not an ideal solution to always have to go back, but it is a solution.

What that doesn’t help you with, and this is something that the Israelis don’t have an answer for, is what if Iran just says, okay, we don’t care about Fordow. We’ve abandoned it. Now we’re going to take the 2,000 or 3,000 centrifuges that we’ve built [at Fordow] and put them someplace you don’t know and then enrich to 60 percent. So Israel has to address that problem in some way. They can’t just walk away and leave the world with Iran having a pathway to weapon-grade uranium production.

How can they cut off that pathway?

You need time to find out where the centrifuges are, where the [uranium] stocks are. You need to be collecting intelligence on the ground. You need to encourage sources inside the program to see the futility of continuing to resist. Iran doesn’t get much from the centrifuge program other than a bomb program. The centrifuges don’t provide any real economic benefit that Iran couldn’t get from buying enriched uranium from overseas [at a much lower than weapons-grade level of enrichment to fuel civilian reactors]. It is ridiculous what they’re doing. I would imagine that many of the scientists and engineers could start to think, why are we doing this? And then they may have insight into secret stocks of centrifuges and weaponization production equipment that’s hidden away. But it takes time.

Tell me about what Israelis hit in Isfahan this week.

Isfahan is where the Iranians convert uranium. If you want to enrich uranium, you need to take it from a mine and then convert it through a chemical process into uranium hexafluoride. The main purpose of Isfahan is to produce natural uranium hexafluoride that then could be enriched. Once you have it enriched you convert it back into an oxide form that could be made into fuel. Iran was building that kind of capability, but stopped … Instead they created a line to start making enriched uranium metal, particularly playing around with 20 percent enriched uranium. They want to create a three-step line to go from 20 percent enriched uranium hexafluoride to 20 percent enriched uranium metal. They claim it’s for fuel, but they have no reactor to put it in.

The three parts of this conversion facility aren’t all done. Only one part was done and Israel bombed it. It really looked like a line to take weapon-grade uranium hexafluoride and turn it into weapon-grade uranium metal.

So this metal would form the hemispheres of the uranium core of a nuclear bomb?

The metal comes out looking like a large hockey puck. Then you would have to melt it in what’s called a vacuum induction furnace, and then pour it into a mold to make the hemispheres. Then you’d have to machine it and do all kinds of other things, like polish it and then coat it—the metal reacts to oxygen and rusts faster than a bicycle handle or a nail. You would have to coat it to protect it, and then it could be used in a bomb. There’s several steps, but it’s a linear process. If you knock out one step, you’ve disrupted the ability to make the weapon-grade uranium component needed for a weapon. Now the question is, does Iran have other capabilities to do that same thing to go from the hexafluoride to the metal? The IAEA thinks possibly, though it’s probably not fully operational or even assembled. You can start to get a sense that Israel is delaying Iran’s ability to make the bomb itself.

[Albright noted that there is an ongoing question of whether Iran has offline vacuum induction furnaces at sites other than Isfahan. Even in light of this lingering ambiguity, he assesses that it would take “months” for Iran to rebuild the Isfahan facility.]

Back to Natanz. How important is this enrichment site, which Israel fully disabled and partly destroyed?

There are over 12,000 advanced centrifuges in the underground hall at Natanz along with 5,000 IR1s [an older Iranian centrifuge model]. And remember, 70 percent of the enrichment effort goes towards getting the uranium to five percent. In Fordow and the Natanz pilot plant [which Israel fully destroyed], Iran can go from five to 60 percent, or from 20 to 60 percent, and it involves many fewer centrifuges, so it can be done in smaller facilities. [Albright said that when Israel hit the Natanz pilot plant, “there were definitely kilograms of 60 percent enriched uranium there.” The facility produced “a few kilograms” of the stuff each month. Around 42 kilograms of 60 percent enriched uranium are needed to produce enough 90 percent enriched uranium for a single warhead, according to the Arms Control Association.]

Fordow is the workhorse, and putting that out of operation is really important. If Iran had to start with natural uranium at Fordow [uranium at zero percent enrichment], breakout timelines would be months to get enough enriched uranium for one bomb. But if they had all the 60 percent enriched uranium at Fordow that’s suspected to be there, just using the advanced centrifuges there, they could have enough for nine bombs in three weeks.

Even now?

Even now. If it’s operational and they have all the 60 percent, they still have a tremendous breakout capability. And that’s why I think Israel needs more time or help.

There’s this line that’s been floating around among some of your colleagues in the disarmament world that an Israeli attack, or really any pressure on Iran, is bad because if you don’t take out the entire program, they’re just going to sprint to a nuclear weapon. Thus, by trying to end the program through military means, you’ll have advanced the creation of an Iranian nuke. Do you think that’s been disproven this week, or is there still the possibility that this whole thing ends with Iran getting what they’ve been working toward for 30 years?

I think those comments are inaccurate. And even before this event, I felt they were inaccurate and politically driven. Their fundamental belief is, We’ve got to stop a war. And it’s ironic that it’s people who in many cases advocate for the abolition of nuclear weapons—but when push comes to shove, when there’s really a challenge and an opportunity to end nuclear weapons, they fold and go, Oh, we don’t want a war. And so in that sense, they’re not very credible. These attacks certainly incentivize Iran to build nuclear weapons. But I think what you’re seeing as this plays out is that Israel is building in many disincentives for Iran to make that decision, along with many roadblocks. But it needs to finish the job. It needs time or it needs help.

What do you think is the most important single thing that the Israelis have done to the nuclear program since their campaign began on Friday?

I think it is collective. They’re significantly setting back Iran’s ability to build nuclear weapons. And they’re doing it in many ways that weren’t expected. And more is to come.