Even before I returned home from serving as an infantryman in the U.S. Army, which included two combat tours in Iraq between 2006 and 2009, I was searching for ways to contextualize my experience.

My questions weren’t ponderous or existential; they were pointed and, I believed, answerable. One was why units like mine were assuming responsibilities far beyond their traditional roles of eliminating the enemy in close-quarters combat. We assisted in the investigation of crimes. We helped rebuild infrastructure. We handed out water and gasoline and worked to reconstruct civil society in a country we knew little about.

I began to wonder, moreover, why my perception of the conflict seemed so far removed from that of nearly every elected U.S. leader. Why did so many in Congress, including vocal liberals, vote for a war that I—a soldier who was actually carrying it out on the ground—was dubious of? There appeared to be a wider spectrum of opinion on the efficacy of what we were doing among soldiers in Iraq than among politicians in Washington. The disputes that did arise in D.C., especially in the early days of the invasion, seemed like exercises in the narcissism of small differences. Why did all the civilians agree with one another?

I’ve been out of the Army for years now, but these questions persist. Why does Obama, for instance, fundamentally sound like congressional hawks when it comes to confronting ISIS? A number of writers and thinkers have been wrestling with similar questions, and Barry Posen, a political-science professor at MIT, is one of them. His latest book, Restraint: A New Foundation for U.S. Grand Strategy, gives a name to the general consensus among the American foreign-policy establishment that I sensed as a soldier, calling it “liberal hegemony.” The term encompasses two philosophies that arose after the fall of the Soviet Union. The first is the neoconservative philosophy of “primacy”— overwhelming military force projected around the world to enforce America’s will. The second is “cooperative security,” embraced mainly by Democrats, which only differs from primacy in that it seeks approval from international organizations like the United Nations and NATO when exerting military force. In both cases, the question is how to use force, not if it should be used in the first place.

Posen’s response is the philosophy of “restraint”—a scaling down of the expectations and demands that decades of liberal hegemonic thought has placed on the United States. I spoke with Posen by phone about his theory and how he would apply it to actors like China, Russia, and the Islamic State. The interview that follows has been edited and condensed.

Scott Beauchamp: Your latest book is called Restraint and the title refers to the “grand strategy of restraint.” What exactly is a grand strategy?

Barry Posen: Pretty much any great power has to operate according to some set of propositions about the threats it faces, the tools it’s going to use to address those threats. Some countries write those down and you can go and read them. They seem quite authoritative. In some countries, it may be a consensus of the elite. It’s not a cookbook that prescribes every action in every situation. It’s basically a set of concepts that outlines threats, discusses political and military remedies, talks a little bit about why those remedies might work, assigns some priorities to threats and to remedies, and it has to be conscious of scarcity. There’s usually some limited amount of resources the state has to spend on its purposes.

My summary statement, which can seem a little airy sometimes, is that a grand strategy is a state’s theory about how to cause security for itself.

Beauchamp: What sort of grand strategy does the U.S. currently have?

Posen: The grand strategy of the United States has evolved since the Cold War ended. It’s not like someone sat down the day after and wrote up something and everyone agreed, but I think through a series of fits and starts, including a series of iterations of actual published statements of U.S. national-security policy that came out of President Clinton’s office, and later out of President Bush’s, we—the elite, the national-security establishment—basically moved to a strategy that I call liberal hegemony.

Beauchamp: What does that mean?

Posen: It means that, in part because of happenstance, the United States found itself not only the most capable state in the world after the collapse of the Soviet Union, but maybe one of the most capable states globally in world history.

I don’t think the United States quite set out to achieve this level of dominance. I think we were just trying to defend ourselves and our friends against the Soviet Union. But we did that so successfully that we drove them out of business. There was no other competitor at the time. So this gave birth to what some people call the “unipolar moment,” where the United States is the world power. And America’s security establishment decided that not only was this a lucky happenstance that provided some new possibilities for the United States, but it’s a situation that could and should be preserved—that we should be trying to remain the preeminent power by quite a wide margin and that you could do this through strategy, through using our capabilities, through various other things that we might do. We could lock in this position and we could write the rules of international politics. And those rules would be essentially liberal. That’s why I call it liberal hegemony.

What does that mean? It means that there will be free trade. Countries should be democratic. Autocrats that repress their people should be opposed. Autocrats that use violence against their people should be overthrown. International institutions which organize cooperation should be enhanced (though the United States should have most of the influence over the rules of those institutions). So that’s the liberal hegemony story: free markets, democracy, and liberal institutions. All spread with the liberal admixture of U.S. power and all kind of organized in a way to help preserve that power position.

Beauchamp: How does restraint differ from liberal hegemony as a grand strategy?

Posen: Restraint starts in part from first principles, from appreciation for a different model of how international politics works, and also reflection on the experience of how liberal hegemony has gone. So we start out from first principals that a grand strategy really is about a theory of how to cause security for yourself, and it takes stock of the American security position.

The irony about the American security position is that the same great power that has allowed the United States to engage in various actions around the world also means that the United States doesn’t really have to engage in those actions. The United States is inherently pretty secure.

The American economy is still the largest in the world. There’s a good chance the Chinese will catch up, maybe by mid-century, but even if they do we’ll still be one of the top two or three economies in the world. And I’m sure if you look inside our economy in 2050 relative to the Chinese economy you probably will still prefer to have ours rather than theirs.

We have a very good base. We have a very good continent as a base, in the sense that it’s well-endowed with natural resources. And who knew that we were going to become sort of energy independent again. We had the great energy crises in my time, the fear about dependence on the Persian Gulf. All that sturm und drang seems to have been overtaken by the intersection of American know-how and the endowments of the continent.

There’s where we are. We have big oceans to the left and right and relatively weak and pliant neighbors to the north and south. This means that we have a very good security position inherently. Even before the invention of nuclear weapons, it was pretty hard for another country to think about invading the United States.

We’re a nuclear-weapons state. We have the best nuclear force in the world. Anybody who attacks us with nuclear weapons is going to get incinerated. That’s cold comfort, because we’d rather not be incinerated ourselves, but it puts the onus of craziness on someone else who really has to take a huge risk to use nuclear weapons on us. It’s another barrier to countries coercing or conquering the United States.

Beauchamp: But isn’t a large part of America’s economic security based on maintaining global stability?

Posen: Even if you look at the pattern of our trade, people worry that our GDP depends so much on world trade. First, it doesn’t. It’s meaningful. World trade is definitely meaningful. But about a third of our trade is in this hemisphere. It would be very hard for things abroad to wreck that. And the rest of our trade is pretty much divided across a number of trading partners. So, many, many bad things would have to happen in the world for the United States to lose its ability to trade and lose whatever benefits come with that.

Oh, by the way, we have a great military. We’ve been working on it since 1940. It’s smaller than it once was, but we’re on the cutting edge in terms of tactics, doctrine, and technology and new weapons. It costs us a lot to build them and sometimes they’re late, you get your horror stories, but, in the end, when the weapon comes out and it’s finally in the force, it’s usually the best of its kind in the world.

Visitors walk past the Chinese-made Hongqi-2 missile at the Military Museum in Beijing. (Claro Cortes/Reuters)

Beauchamp: What are the real threats to U.S. national security, then?

Posen: It’s reasonable for the United States to pay attention to a small number of threats. We don’t have to transform the world, spread democracy, expand NATO, or any of these other things. But there are a few things that we need to pay attention to. We need what I would call moderate, pragmatic strategies to work on those problems.

One problem is the potential rise of China. In the fullness of time, China may become such a tough competitor that we need to contain it the way we contained the Soviet Union. Is that time upon us? I don’t really think so. China is asserting its interests in its own area, mostly its coastal areas, a little bit on its land periphery. It’s a country that’s going through rapid change. It’s got a lot of internal problems of its own. It’s got a lot of security problems. Its military isn’t gigantic.

Beauchamp: Does the United States need to pivot to Asia?

Posen: No, not really. Even if we could, it probably isn’t necessary. Quietly shore up a few positions, yes. Get our allies to start thinking about their contributions. One of the bad things about current U.S. policy is that we de-energize our allies from doing anything in their own defense. They don’t actually do enough. We do too much.

If China’s power grows, we need to pay attention to our power too. Our military capabilities have to be adequate to do the things that we might wish to do in that part of the world. Again, with the caveat that some of the things we presently say we want to do in that part of the world are probably unnecessary and provocative.

Two other problems. [One is] nuclear proliferation, everyone’s hardy perennial. I’m less worried about this than some are. I tend to believe the United States could pretty much deter any state in the world from using nuclear weapons against itself, and I think most of our allies who have nuclear weapons can certainly deter the use of nuclear weapons against them. Our allies who don’t have nuclear weapons, who are relying on America’s extended deterrent commitment, given the kinds of challenges they face, the commitment is reasonably credible right now.

So I don’t think proliferation in the sense of new nuclear-weapons states is a gigantic problem. It’s good that the United States has policies that try and slow the rate of the emergence of new nuclear-weapons states, because it takes time for countries to figure out how to build these things, but more importantly how to take care of them. It takes time for others to figure out what difference it actually makes, whether they should be in a panic. So slow proliferation is better than fast. No proliferation is probably the best of all, but probably can’t be achieved. Nuclear weapons are just too easy to build. The technology is not that esoteric. It’s an old technology now.

So really, our objective should be to keep nuclear weapons in the hands of states, and to be sure that states use best practices in terms of safety, security of their arsenals, that they have robust and reliable command and control.

Beauchamp: This applies even to Iran?

Posen: I would be against waging preventive wars to keep Iran from having a nuclear-energy infrastructure. This is a remedy that’s way beyond the nature of the problem. However, there is a potential problem, which unfortunately we haven’t confronted, which is the possibility of nuclear weapons falling into the hands of non-state actors who cannot be deterred because many of them have no base. And they may be so ideologically extreme that they don’t care about the consequences, even to their own friends, of using nuclear weapons. Using a nuclear weapon—because that’s what we’re really talking about here. That’s something we really should be very concerned about. This is why I think the United States should be more active in working with other countries on how to secure their arsenal, to secure their stockpile to prevent smuggling and theft of materials. It’s very intelligent for the United States to pay attention to that because those are the things that you should do to ensure that nuclear weapons stay out of the hands of groups that may not be deterrable in a conventional sense because they have no return address.

And this relates directly to the third problem, because those groups are the kinds of groups that are dangerous even if they don’t have nuclear weapons. Some kinds of terrorists, and we’ve seen one group, al-Qaeda, they have global ambitions, and they’ve identified the Americans as the principal barrier to whatever political or even religious vision they have. So they’re willing to accept a lot of risk and do a lot of damage, and we need to be on guard against such people. We ought to have learned that lesson. I can’t say that I was prescient about it before 9/11, but I hope I get it now.

New Yorkers watch the collapse of the World Trade Center in 2001. (Ray Stubblebine/Reuters)

Beauchamp: But then the question is, how do you deal with terrorist groups?

Posen: My view is that defense is more important than offense. Intelligence, police work, surveillance, airport security, ship security, port security—these are things we have to pay close attention to and we have to cooperate with others to do it, because these other countries, rich countries, are in the sights of these odd groups, murderous groups, and so they have an interest in cooperating, and that’s where most of the effort should go. Does there need to be some offensive effort? Yes, probably. How much? Just enough to keep those guys worrying about their safety, so they’re spending resources in order to avoid being killed or destroyed.

I don’t have high hopes that we can go and extirpate these groups, and particularly that we can reform the societies that seem to give birth to them. I don’t think we’re going to so reform the entire Islamic world that we’re going to make it impossible for such groups to reemerge. This idea that you’re going to turn Afghanistan into a democracy, that you’re going to turn Pakistan into a democracy—well, Pakistan is a kind of democracy, that’s insulting, but it’s not a perfect one—you’re going to turn Iraq into a functioning democracy, you’re going to conquer the areas where ISIL [also known as ISIS, or the Islamic State] now is, annihilate ISIL, and that no one is going to survive to come back and attack you yet again 10 years from now, to me this is all fatuous.

Beauchamp: In my own experience on the ground in Iraq, when you fight against an insurgency, you tend to create enemies just as, if not more, quickly than you destroy them.

Posen: The more you try and extirpate these groups, I think, you create a lot of negative energy out there that generates new groups against you—new followers for old groups, new followers for new groups. Not to mention the odd interaction effects where, by fighting some of these groups, we’re running a kind of school for them. The ones who survive the first school are tougher in the second. So now most of the people who lead ISIL apparently passed through our jails. People fought us in Iraq, were in our jails in Iraq, got to know each other in those jails in Iraq, who knows what else they learned in those jails. And after awhile we spring them, because if we take 20,000 prisoners, we can’t keep them, we can’t house them all in Guantanamo, and we can’t kill them. So, we’re giving people a graduate education in conspiracy. And we’re giving them good reasons to hate us. So it’s a perpetual motion machine. If you try to go out and reorganize their societies at the point of a gun, I think it’s a losing proposition. We tried it a couple of times and it failed. And we’re getting ready to try it again, apparently. Apparently we’re so powerful that we don’t need to learn.

Beauchamp: How would a strategy of restraint deal with Russian encroachment into Ukraine? Is that an EU problem? An American problem?

Posen: You use the word ‘encroachment,’ but I think we have to be specific here. Let’s just talk about the worst case. Not because I treat the worst case in a cavalier way, or because I don’t feel for people, or because I don’t know that there won’t be some cost associated with it. Let’s say that Ukraine just implodes and that the Russians just came in and took the place, occupied it, made it the Republic of Russia, or whatever they would do again. How much new danger would that create for U.S. national security? I think the answer is almost none.

Now that said, would it create new dangers for European security? Yes it would, because Russian ground forces, Russian nuclear forces, almost everything would move forward and would now be on the borders of the European Union and the North Atlantic Treaty Organization. We would have recreated the old inter-German border, the old NATO/Warsaw Pact competition, with Russian and American and NATO forces nose to nose along a very long line of contact, we’ll call it.

Beauchamp: Is that a better world?

Posen: No, it’s not. I think it’s not a better world. Is it a world in which because of our present treaty commitments the Americans have some commitments to bolster deterrence in that world? Yes it is. Unfortunately it is. I wish it were not, but it is, because of commitments that were made—commitments that I opposed, but were made, and are done. They’re baked into the cake.

That’s a problem. We’d rather not face that problem. It puts us in a situation where, because our forces are in contact again, it means the risk of nuclear war between Russia and the United States is actually raised a little bit. It’s all bad. OK, is it bad enough, given our successful record of having dealt with such a situation, that the United States should be willing to lead the NATO alliance in war to prevent the Russians from absorbing Ukraine? I think the answer is clearly no. And I think even the American hawks know it. Because when you heard the American hawks talking about Crimea, you heard most of them say, usually at the end of their long disquisitions on the subject, that this was not an occasion for the United States to wage war. So I think they’re admitting that, yes, there is an interest here, but the interest does not rise to the level of something that should be worth fighting for. And why is that? It’s not a vital interest.

Beauchamp: What is a vital interest?

Posen: A vital interest has something clear and substantive to do with your national security. Now, if Russia were to be strong enough again and aggressive enough again, and the Europeans were to be supine and incompetent enough that it looked like the Russians were going to conquer all of Western Europe and create some new Putin Napoleonic empire, yeah, that would be a threat to American security. We should act to oppose that. But have you looked at the stats on Russia lately? The stats on their GDP, the stats on their demographics, the stats on the actual size of their military power even on their best day? Is it even remotely plausible that these people are in a position to make a bid for hegemony in Europe? No, it’s not. It’s not remotely plausible.

People draw analogies to 1935 or to 1914, in the sense of a sort of big, revanchist, capable state that can carry all others before it, but I don’t think that’s the Russia we see.

I think that the Russia we do see is a state that’s certainly capable enough to assert its interests on its own periphery. And that’s what it’s doing. And in that sense, it’s much stronger than it was in the early 1990s, when the Americans could kind of shape things the way they wanted, expand NATO without opposition, because Russia was prostrate. But it’s not prostrate anymore. It’s a country. It has a leader. It has an economy. It has rebuilt a military that can actually do some things. It’s still a major nuclear-weapons state. And that means that it’s going to assert some interest in its neighborhood. And that means we have to think about how much those interests really matter to us, and how much of those interests we should accommodate.

We don’t have to accommodate by shaking hands and saying, “we bless this acquisition.” We just have to accommodate. I think it’s quite clear we’re going to accommodate on Crimea. And there’s your statement about how serious it is to U.S. national security. It isn’t.