One of the hardest problems facing president-elect Donald Trump as he prepares to take the reins of the U.S. government will surely be the conflict in Syria. Trump has drawn up the contours of a new Syria policy that would shift away from trying to topple Syrian President Bashar al-Assad, in favor of a military campaign more tightly focused on the self-declared Islamic State and other jihadi extremists.

However, Trump’s proposals have been thin on detail, and his advisors and early picks for senior office have espoused conflicting views on the issue. It seems likely that Trump will initially be forced to pick up where President Barack Obama leaves off in January 2017 and plan out his course adjustments as he goes. That, in turn, means that Obama’s Syria policy is likely going to inform Trump’s own understanding of the conflict and constrain his future options, at least in the short term.

To gain a better grasp of how Obama approached the Syrian conflict—which engulfed much of his attention and, he says, haunted him constantly—Diwan spoke to Derek Chollet, a former high-ranking official in the outgoing administration. After serving on secretary of state Hillary Clinton’s Policy Planning staff from February 2009, Chollet moved to the National Security Council in 2011. From 2012 until 2015, he worked as assistant secretary of defense for international security affairs. He thus helped shape U.S. Syria strategy in a period that spanned several crucial developments, including the tense intra-administration debates over whether to arm the Syrian rebels or not, how to respond to the Eastern Ghouta chemical attack in August 2013, and how to address the rise of the Islamic State.

Chollet now serves as a counselor and senior advisor for security and defense policy at the German Marshall Fund of the United States, a Washington-based think tank. He is also the author of a new book called The Long Game: How Obama Defied Washington and Redefined America’s Role in the World. The interview took place before the U.S. elections.

Aron Lund: When the Syrian crisis erupted in 2011, U.S. policy seemed to hinge on the idea that President Bashar al-Assad would fall almost regardless of what the United States did or didn’t do. Is that a fair description, and, if so, was the fact that he remains in office an intelligence failure?

Derek Chollet: In the very beginning of the crisis in 2011, there was a sense that this was another chapter of the Arab Spring. It started as a peaceful protest against Assad, who responded violently, and war spiraled from that point. Back then, there was a sense that Assad wasn’t necessarily on his way out the following week, but certainly that he was losing power and losing control over his country—which, of course, he was. If you look at Syria now, he has lost control over large swaths of the country. I don’t know about percentages, but he is perhaps down to 4050 percent of the country now.

At the time, looking at Syria in the context of Egypt or Libya and the instability that was emanating from elsewhere, there was a feeling that Assad’s days were numbered. The only way he would stay in power was if he continued to receive support from abroad and resorted to violent means. Of course that is exactly what happened.

AL: Later in 2011 and early 2012, the crisis in Syria mutated into an armed conflict. At what point did you first begin to discuss U.S. military involvement, whether direct intervention and the imposition of a no-fly zone or by arming the armed opposition and providing training?

DC: I can’t remember the precise point, but certainly by mid-2012. There was both the issue of greater direct U.S. military involvement and protecting Turkey or Jordan, and a debate about how to handle the opposition and whether to support it in various ways. By mid-2012, this discussion was very much under way.

Still, there were two pieces of the discussion. They were related, but from the perspective of our interests, we looked at each of them a little differently. The first was the issue of chemical weapons. By 2012 and 2013, it was certainly the overriding concern of the administration. What do we do to ensure that 1,300 tons of Syrian chemical weapons are not used or end up in the wrong hands? It was a concern of ours, but also of the Israelis, and of others in the region.

This was related to, but still somewhat separate from, the question of what to do about Assad and the conflict itself. One way in which these questions were related was that in so far as you had some who advocated using military force to overthrow Assad—but they were not many within the administration—the disposition of Syrian chemical weapons after the fall of Assad would be much on our minds.

AL: But even if the United States government was not involved in arming the rebels very early on, it seems others were. I’m thinking of Turkey and Qatar. This was well before summer 2012. How did the United States respond to this?

DC: Well, yes, clearly the Arab Spring became a proxy war for various regional powers. From our point of view, we faced the question early on about, well, who is the opposition? Who are they as individuals? What is their agenda? How can we ensure that any support will go into the right hands, and so on? Those are all questions that we had to answer according to the law, not solely as a policy matter.

Many other countries do not have those types of restrictions. We had partners who were just throwing all sorts of resources at the conflict. Many of those resources ended up in the wrong hands. It was very much in the spirit of “the enemy of my enemy,” and to some or our partners it didn’t matter if their support ended up with Jabhat al-Nusra or other groups. So we spent a lot of time on trying to persuade them to support the moderate opposition and galvanizing the international community to empower the moderate groups.

AL: In spring 2013, the United States announced that it would provide direct support for certain armed insurgent groups. This was framed as a response to Assad’s use of chemical weapons, after many reports of small chemical attacks. Was that true, given that this coincided with Hezbollah’s open entry into the Syrian war and other issues?

DC: The White House framed it publicly at the time as being in response to the chemical weapons, and that was true. But our thinking and understanding of the opposition had also advanced at that time. We had learned more and we were more confident that the supplies we would provide would stand a chance of bringing about the desired results, not just make things worse. But the White House announcement in spring 2013 was framed as something we did in response to, among other things, the reports of usage of chemical weapons.

AL: And were you sure at the time that this was indeed Assad using these weapons, because, of course, the Russians claimed the opposite?

DC: Yes. Sure.

AL: Then came the big nerve gas attack in the Eastern Ghouta on August 21, 2013. This is where the Obama administration has been most severely criticized, for seemingly not enforcing its “red line” threat. What is your view on this?

DC: Well, this is the whole first chapter of my book, so I would advise those interested in a longer version to look that up.

There is no question that the red line episode is used by Obama’s opponents and, also, by many folks who support the president but advocate for more U.S. military involvement in getting rid of Assad. I look at it differently, being someone who spent a lot of time worrying about the future of Syria’s weapons of mass destruction.

As a country that went to war in 2003 over a weapons of mass destruction threat that we later discovered did not exist, which caused problems with which we are still grappling, I find it interesting that Obama is now being attacked for dealing with an actually existing weapons of mass destruction threat. One which, by the way, was a lot worse than what people feared we would find in Iraq.

Of course, in retrospect, there are things we could have done differently in Syria along the way, short of a full-scale invasion. But still, if Obama had “enforced the red line,” he would only have been able to deal with a small fraction of the chemical weapons arsenal. And if, God forbid, some of those weapons would then have been let loose, or used by others, or used elsewhere, he would have been held accountable for that. I’m sure that if Obama had done that and moved forward, and something would have happened, he would have been held accountable. People would have asked, Why did Obama use force just to protect his honor after having laid down the red line, when he had this [Russian] deal [to remove Syria’s chemical weapons arsenal] in front of him? In the end, you can argue that it was inelegant or an ugly win, but the outcome made us all safer.

AL: Still, many of the people who criticize Obama over his 2013 decision are not looking at this from the weapons of mass destruction angle. They see it in terms of the effect on Syria and on the efforts to remove Assad. In practice, the chemical weapons deal led to the Geneva II talks in early 2014 and to more interaction with the Russians. For good or bad, the United States seemed to step back from confronting Assad. Would you agree with that description?

DC: It is not a question of whether the United States can overthrow a government or not. We have proven many times over the past few decades that we can. The question is what comes next.

Look at Libya today. There, we now confront the question of whether we should have gone in in the first place. Now, some say—and I’m not one of those people, by the way—why did we do it? They say it was unwise. Then there is the question of how the United States and the Europeans mishandled the post-Gadhafi period. Perhaps we should have put some troops on the ground, even over the objections of the Libyan government at the time? It’s important to understand that in Syria we were all coming from this. We had just confronted the Libyan question, which was much on our mind at the time.

Often, the debate is framed as “doing something” or “doing nothing.” That’s not true. We did a lot of things. We deployed military assets to Jordan and to Turkey. We began supplying the opposition with considerable amounts of assistance. We worked with partners in the region to help the opposition defend itself militarily.

Perhaps, in retrospect, we could have tested the risk of escalation further. But the most difficult question, for which Obama constantly sought an answer, was how to prevent this from escalating into a conflict for which the United States would be held fully responsible and that would envelop U.S. foreign policy for years to come. Iraq did envelop our foreign policy through the last decade and we wanted to prevent that from happening again. I don’t think that is misreading history. It is to have learned from history.