On Monday, Donald Trump chose Lt. Gen. H.R. McMaster as his new national security adviser, less than a week after Michael Flynn was forced out of the position. McMaster is known as one of the Army’s top strategists and intellectuals and has become as famous for critiquing military strategy and bureaucratic thinking as for leading troops in battle. In short, he may not appear to be a very Trumpian choice, which makes him an especially intriguing one.

To discuss McMaster, I spoke by phone with Andrew Exum, a former deputy assistant secretary of defense for the Middle East in the Obama administration and a contributing editor at the Atlantic, who has known the lieutenant general for more than a decade. During the course of a conversation, which has been edited and condensed for clarity, we discussed McMaster’s ideas on warfare, why Trump made the choice he did, and the importance of giving the president honest advice.

Isaac Chotiner: You tweeted on Monday that it was not an exaggeration to say that “the world should feel a little safer today.” Why is that?

Andrew Exum: I just cannot say enough good things about H.R. McMaster. It sounds like hyperbole when you start to describe the man. He is one of the most talented officers the United States Army has ever produced. He has distinguished himself in two very different conflicts at two different levels of command. In the first Gulf War he led a troop of armored cavalry, and in Tal Afar in 2005 he led a brigade. He was arguably the most outstanding company commander in the First Gulf War and the most outstanding brigade commander in the Iraq war that followed. In between, of course, he received a Ph.D. in military history from the University of North Carolina. His dissertation became a best-selling book, Dereliction of Duty, which I very cleverly only read about two months ago.

That book was about the way the military dealt with the Johnson administration during Vietnam, yes? What was the general thesis?

Yeah. It was scathing in the way it discussed the Joint Chiefs and the way in which they provided advice to the president. But what I keep going back to when thinking about the book is the criticism of the national security decision-making process in both the Kennedy and Johnson administrations. The reason I am thinking of this is because, as a friend of mine pointed out, this decision of Trump’s is like bringing in Ben Bernanke to be the head of the Federal Reserve right before the Great Recession. H.R. McMaster very carefully and often caustically studied the national security decision-making process, and now he is responsible for that process. He’s a real intellectual.

He was also influential in shaping David Petraeus’ strategy into how to wage war in Iraq. What was his large idea there?

H.R. has this line, and I think he is quoting someone, about war being the ultimate arbiter of fighting institutions. His point is that you can go in with these great theories about how war is meant to be fought, but it’s really in combat that you find out how good the institutions you built are. H.R. was one of a group of commanders who came into the Iraq conflict and saw that the army we had trained was not up to the task. And to his credit, he did things differently in Tal Afar. H.R. was someone who, in an isolated area with Tal Afar, which has some of the most complex demography in Iraq, was able to wage a successful counterinsurgency operation, at least for a while, because when his unit left it was replaced by a smaller unit.

A lot of what H.R. gets credit for is all the stuff about listening to the population and trying to isolate the grievances and see what is driving the conflict. But quite frankly you should also not understate the “clear” part of what he did, in terms of “clear, hold, and build.” He put a berm around the city itself and fought like hell. He got as many civilians out as possible and then fought a very hard battle to seize Tal Afar and then to hold it. But the way in which he did it was somewhat revolutionary. It was a very patient approach to pacification and rooting out the enemy, and doing so in a way that alienated as few Iraqis as possible.

The portrait you are painting is not obviously a picture of someone Trump would like. What do you think Trump might see in him?

H.R. does not, when you talk to him, come across as an egghead intellectual. He is a big, bullish man, who takes up a lot of space in the room and has a very powerful personality. He projects strength personally, which is probably one of the reasons he is so admired and beloved by the troops who served under his command. Knowing the president, I could see him liking that.

In addition, I have little doubt that many of the people [Trump] was speaking to, including Petraeus, no doubt had very good things to say about McMaster. He is a known quantity. If you were to take the pulse of a dozen national security leaders of both parties and asked them to come up with a list of the five smartest officers in the military, H.R. would be on the list.

Without asking you to reveal private conversations, you aren’t describing someone who would seem to like Donald Trump. Is this just a job you can’t say “no” to? Do you think they might have something in common ideologically that you aren’t aware of?

They could. I have never had an overly ideological or political conversation with H.R. McMaster. He has never struck me as a man who has the type of pungently ideological views of a Steve Bannon. But bear in mind that he is a three-star general who has been asked to do one of the most difficult tasks in the United States government. I can imagine that it is very difficult for him to turn down this job. If anything, given his academic research, and how deeply he cares about this country, and given the oath he has sworn, I couldn’t imagine he would have ever said no.

How far do you think this will go toward placating people in the national security bureaucracy who are warring with the new administration?

I think it’s too early to tell. There are a lot of things driving the animosity between Trump and the bureaucracy. One of those things is that you had a national security adviser who was not necessarily listening to his staff and was a bit overwhelmed with the job, based on folks with whom I have spoken. But the other thing is that this is still very early days in the administration, which has fallen behind the pace in terms of putting their appointments in to Defense and State, and as a result, the folks on the National Security Council are understandably worried and don’t really have leadership. I think the animosity that you are seeing will start to recede once some Trump administration officials come into the departments and agencies and people see that most of them are reasonable. I personally saw the temperature at the Department of Defense go way down after Jim Mattis was made the secretary.

OK, but he is one of the few sane people Trump has put in though.

I don’t think that is true. I think that Tillerson, quite frankly, has the potential to be an excellent secretary of state and has the potential to provide the type of management for the organization that you were never going to get from a John Kerry, for example. And I also think that even when you scratch off all those people who said they would never work in a Trump administration, I think that this administration can still find a lot of talented people to serve at the deputy-assistant and assistant-secretary levels. There is talent out there, and I don’t just mean smart people, but people who can be good managers. But we’ll see. The loyalty test this administration is applying is a bit worrisome, to say the least.

I think for a lot of people this was particularly soothing, because as much as people respect Mattis, this guy will be in the building with Trump every day.

That’s right, and maybe I have too much faith in him, but frankly McMaster has staked so much of his intellectual credentials on the need to deliver blunt and honest advice to the president that it would be ironic and sad if he himself didn’t do that, but I think he will. It is no exaggeration to say that I will sleep better tonight.

Or sleep better for at least two months, which is how long he will last giving honest advice to this president.

Well that’s right. One of the great things is that we do have some leaders in place, not just Mattis and McMaster but the chairman of the Joint Chiefs, who are real men of integrity. If things get too bad, I can’t imagine them having too much patience, although it is always tempting to convince yourself that, “Oh, I can do something great” and stay on past the time you should have resigned. But I have great faith in him.

Thank you, Andrew. Hopefully humanity will now survive long enough for us to do this again.

Inshallah.