ASPEN, Colo.—Retired U.S. Army General David Petraeus pioneered America’s approach to counterinsurgency, led the surge in Iraq, served as director of the CIA for a year, and was sentenced to two years probation for leaking classified information to his mistress. On Wednesday at the Aspen Ideas Festival, he was interviewed by my colleague, Jeffrey Goldberg, about subjects including efforts to stop Iran’s nuclear program; the civil war in Syria; ISIS and the threat it poses to the United States; and the Iraq War.

Here are several noteworthy moments from their conversation, slightly condensed:

The Risks of Attacking Iran

Jeffrey Goldberg: So you believe that, under certain circumstances, President Obama would still use military force against Iran?

David Petraeus: I think he would, actually. I know we’ve had red lines that didn’t turn out to be red lines. ... I think this is a different issue, and I clearly recognize how the administration has sought to show that this is very, very different from other sort of off-the-cuff remarks.

Goldberg: How did the Obama administration stop Israel from attacking Iran? And do you think that if this deal does go south, that Israel would be back in the picture?

Petraeus: I don’t, actually. I think Israel is very cognizant of its limitations. ... The Israelis do not have anything that can crack this deeply buried enrichment site ... and if you cannot do that, you’re not going to set the program back very much. So is it truly worth it, then?

So that’s a huge limitation. It’s also publicly known that we have a 30,000-pound projectile that no one else has, that no one else can even carry. The Massive Ordinance Penetrator was under design for almost six years. ... If necessary, we can take out all these facilities and set them back a few years, depending on your assumptions.

But that’s another roll of the iron dice, as Bismarck used to say, and you never know when those dice are rolled what the outcome is going to be. You don’t know what risks could materialize for those who are in harm’s way.

You don’t know what the response could be by Iran.

There’s always the chance that there will be salvos at Israel, but what if they decide to go at the Gulf states, where we have facilities in every single one.

This is not something to be taken lightly, clearly.

Is Iran or ISIS a Bigger Threat?

Goldberg: I interviewed Ben Rhodes, who is the deputy national security advisor. Later that same day I interviewed Lindsey Graham. I asked them both the same question: Who is more dangerous to American national security—the Iranians (the Revolutionary Guard Corps of Iran), or ISIS. Ben Rhodes said, without hesitation, ISIS. Lindsey Graham said, without hesitation, the Iranians. Where do you fall on that?

Petraeus: Interestingly, I think Ben is right on the threat to the United States. The ISIS threat in the region, the Sunni extremist threat to our allies in Europe and elsewhere in the world, and indeed to our own homeland––I mean, we’ve seen recent examples of what appear to be orchestrated attacks, and there certainly is a trepidation of this upcoming holiday that is a bit heightened over recent years.

But, of course, Senator Graham is right ... that in the region, the Shia militias, the proxies for Iran, are very dangerous. You sense, in fact, this possibility of an all-out Sunni-Shia civil war.

Goldberg: How dangerous is ISIS to the United States right now?

Petraeus: The danger to the United States right now is that they are seen as a successful organization, and nothing succeeds in the online recruiting business like success. And just the sheer proselytizing they can do on the Internet with people who are almost trying to self-recruit.

It doesn’t take much, with what you can buy at a gun show in America, if you can open up on a mall or some public place that’s full of people. So it’s a significant danger. I don’t think it’s anywhere near the sophistication of a 9/11 attack. And to our allies, we’ve seen very vividly what has been done in Europe as a result of ISIS recruiting.

The Advice on Syria That David Petraeus “Theoretically” Gave as CIA Director

Goldberg: In Syria ... was it a mistake not to [help arm and support moderate anti-regime rebels] in 2011?

Petraeus: If I had advised something at that time it would have been covert action, given where I was [head of the CIA]. And so it’s not something that I can talk about now. The New York Times certainly has the memoirs of some of the other participants.  

Goldberg: So theoretically, if you had been running the CIA in 2011, you would theoretically have advocated for that?

Petraeus: Theoretically.

Goldberg: OK, just wanted to check.

Petraeus: Aggressively.

Goldberg: OK.

Petraeus: Actually, it was a little bit later. But I can neither confirm nor deny.

Goldberg: He’s not actually here at all by the way. You’re not even seeing him. It’s a hologram.

Petraeus went on to say that today, the United States needs a force in Syria that it can support, but that it is not in America’s interest to prop up the Assad regime.

Did the Iraq War Destabilize the Middle East?

Goldberg: Go back to 2003. Were we inadvertently a triggering mechanism for everything that came next?

Petraeus: I’m not so sure that we were, actually. If you think about it, these didn’t happen until a decade later. I can’t for the life of me think of the link between Iraq and why a fruit vendor self-immolates in Tunisia and cracks this seemingly solid crust that turns out to be so fragile that societal unrest touches off.

And you see this in Egypt as well.

[Former Egyptian President Hosni] Mubarak would meet with me when I was at Central Command. He would lean and put his hand on my knee, as if a father figure, and say, “General, don’t ever forget the Arab Street. Listen to the Arab Street.” I’d like to go to him now and say, “Mr. President, what about that Arab Street, what’s that all about?”

Is America in Decline?

Goldberg: There’s a feeling that this presidency is as much about underreaction as the last one was about overreaction. There’s a lot of talk about the dispensability of the United States. We can’t do everything. China is rising. We have to manage that. Are we in a period of decline? Is that sort of decline the worst thing in the world for the United States?

Petraeus: America is not in decline. When you experience firsthand these very visceral wars that we’ve been through, costly, frustrating, long in duration, setbacks, it’s understandable, I think, that the pendulum swings in the other direction. ... I think ISIS brought it back. I think the beheading of an American is a big deal, the public reacted to that and so did their leadership, and we now recognize the threat that is posed.

I was in London recently and I was asked, after the American century, what? I think they expected me to say the Chinese Century, the Asian Century, or whatever. And I said, after the American Century, the North American decades. Now that’s not a single decade, and it’s not a century. But we have this extraordinary opportunity, because of the energy revolution, which has really upended global energy markets: we’re now the number one natural-gas producer, we’re the number one liquid-oil producer. ... I know there is an insurmountable comparative advantage in that.