You are at almost 95 percent. At some point it goes down. So maybe Barak said, ‘if I don’t have 95, it’s zone of immunity.’ I say no. It is fading down gradually and slowly. Yes, it is declining. And there is a point on this slope—60 percent, 50 percent—where you say launching an attack doesn’t make sense. You still can stop them. You may delay it instead of three years, two years. Instead of two years, a year and a half. So again, it’s not binary.

BB: But Barak sincerely believed—and I guess Bibi didn’t believe it because he didn’t launch the attack—that 2012 was the end date?

AY: Yeah. Maybe he said that in 2012, it’s something like this [Yadlin draws a line on the graph at the end of 2012 with a rapid downward slope]. And I always said it’s something more like this [drawing a more gradual descent].

BB: Has Israel started descending on this graph, or is it still here [pointing to 95-percent mark]?

AY: I think we’re still here. But not for long. That’s what I’m saying. Let’s say this is the line of negotiations. Don’t let Rouhani take it all the way here, to the lower-percentage area. You have to end the negotiations within a short time frame. This is September, so let's aim to understand where the negotiations are going in the coming few months.

BB: How about the issue of Iranian retaliation? Obviously it’s hard to anticipate how things will play out, but what would you say is the median scenario—in other words, it could turn out better, it could turn out worse—in terms of Iranian and Iranian-proxy retaliation in the event of an Israeli strike?

AY: I think we’ve discussed it many times. There are two schools of thought. One speaks about “doomsday” and “the Middle East in flames” and “World War III.” And there is a second school of thought, which I am part of, the bottom line of which says that there will be an Iranian retaliation. It will be measured, calculated, and limited—both because of capabilities and more because of motivation. Because the Iranians know that their retaliation is only the second round, that there will be a third round against them which will be much more devastating. The first round will be limited to a surgical attack on nuclear facilities. There will be no damage to the Iranian economy or the Iranian population. After the Iranians retaliate, if they retaliate strongly—which I doubt that they have the capability to; they do have the capability to retaliate, but as I said, limited—but assuming they are doing all they can, they have to anticipate a retaliation from the other side, which now will not be limited to nuclear facilities. They can hit their oil facilities. They can hit their gas pipelines. They can hit their air force, their navy, the leadership, everything. So I don’t think the Iranians will have the motivation to start a full-scale war.

BB: So you don’t expect them to retaliate against U.S. assets in the Gulf?

AY: When we look to the future, we have to be humble. We have to understand our limitations in forecasting the future. It is much easier to tell you from an intelligence point of view how many centrifuges are spinning and how many kilograms of uranium have been enriched because these are engineering terms—if you have good sources, you know the answers. The answers about future decisions of political leaders and generals are not 100 percent, so you have to be careful. But I think it makes no sense that Iran would retaliate against the U.S. in the Gulf if another country attacked Iran because then they would bring upon themselves a devastating reaction.

BB: I want to get back to the issue of the breakout period. How long would it take the Iranians to produce a bomb if they decided to go for one tomorrow?

AY: I can give you a very good rule of thumb. If you take low-enriched uranium, you feed it into 3000 centrifuges, after a year, you get enough highly enriched uranium for one bomb. This is the rule of thumb. Now let’s say the Iranians have 12,000. So how long will it take them?

BB: Three months.

AY: Very good. Let’s say they will have 60K? Two to three weeks.

BB: And how many centrifuges do they have now?

AY: According to the IAEA’s last report, they have about 15,000.

BB: But all centrifuges aren’t created equal, no?

AY: This equation is for P1, Pakistani-design centrifuges. With IR2—Iranian design, which is an advanced centrifuge, you need only 1,000 instead of 3,000 to enrich enough fissile material in one year for one bomb. Which makes it even worse because they have by now, I think, plus-minus 1500 advanced centrifuges.

BB: So if they have 15,000 or so total centrifuges, then the breakout period is less than three months?

AY: Once again, don’t try to do the exact math. Enrichment is not the only point. Basically, enrichment, it's couple of months—two months, three months. But I will complicate it a little. To achieve a bomb, you need to enrich 25 kilograms of uranium to a military-grade level, but you also need to complete the weaponization process. So you may think that now getting enough highly enriched uranium is no longer the bottleneck. Weaponization may be. Let’s say weaponization takes four months. So now it’s not so important whether it’s two or three months for enrichment's breakout. And on weaponization, the numbers are much more varied. On the enrichment timetable, all the engineers will agree. This is not the case for weaponization.

BB: So for weaponization, it could be anything from a day to a year.

AY: Exactly. Depends how much knowledge they have, how many experiments in dual-use components they’ve made. You can’t say between a day and a year, but you can say between two months and a year and a half.

BB: So you think this is underrated as a factor? It seems like everyone focuses on breakout, and weaponization might be the underappreciated variable.

AY: Absolutely. This is now the thing to look at. But once again, some people will say, ‘OK, so one bomb. What will they do with one bomb? Let’s measure it for an arsenal of three bombs, five bombs.’ Then it takes a little bit more time.

BB: Would they go, in your judgment, for just one bomb?

AY: If they want the bomb as an insurance policy, one bomb is enough. They have learned from North Korea that you get one bomb and then nobody touches you. But you can have another person who will say, ‘So what if they will have one bomb? One bomb is not operational. We can destroy it.’ But the conventional wisdom is that if they have one bomb, then the battle is lost. So the calculations are for one bomb.

BB: Why, for the sake of argument, can’t Israel live with a nuclear Iran? What’s wrong with Mutually Assured Destruction?

AY: It’s not an issue of MAD. Israel is a very very small country. It is not Israeli experts who say this. It’s an Iranian ex-president, Rafsanjani, who said in 2001 that Israel is a one-bomb country and that a proud Iranian or Islamic nation can absorb two or three bombs. But it’s much more than that. There is the issue of miscalculation, unintended escalation—the fact that unlike in the Cold War between the U.S. and Russia, we don’t have mechanisms to de-escalate. We don’t have a telephone hotline between Jerusalem and Tehran. We don’t have embassies like the U.S. embassies that helped defuse the Cuban missile crisis. The most problematic issue has nothing to do with Israel. It’s nonproliferation in the Middle East. It’s the fact that the Saudis, the Egyptians, and the Turks will go for nuclear weapons if Iran gets them, and all I have said about miscalculations, unintended escalations, nuclear weapons to terrorists will be multiplied tenfold—it will be a nuclear nightmare. And let me remind you that the terrorists in the planes that flew into the towers in New York City on September 11 were not Iranians. They were Saudis and Egyptians. So the idea of everyone having nuclear weapons is not a good idea.

BB:If you had to bet your life on it, do you think Israel will launch a strike in the next year?

AY: I am not in the business of betting. It depends on some important future developments, and the leading factor is the negotiations and the parameters of any future deal.

BB: But you’re saying it’s wrong to think that Israel has another year to stop Iran.

AY: It’s more correct to say that the next year, unlike previous years, is really the year of decision. Decision is not necessarily an attack—it can be an attack, it can be leaving the problem to Obama to solve, a decision to live with problematic deal, or a decision to live with the bomb, with all its ramifications.

Ben Birnbaum is a writer living in Israel. Follow him @Ben_Birnbaum.