Our initial response was unsatisfying: Obama decided to publicize a decision to provide military support to the Syrian opposition. Almost by default, the responsibility for announcing this fell to me. By then, I had been a deputy national security adviser for nearly four years, and was known to be someone who was particularly close to Obama. Even though I had misgivings about our Syria policy, I wanted to do something about the catastrophe in Syria, just as I had advocated intervention in Libya. I had also internalized a certain ethos: If there was an issue that no one wanted to talk about publicly, I would do it. I thought it was part of my job, as Obama deserved to have someone willing to defend him. I sensed, though, that it would cost me, allowing me to be blamed for decisions I didn’t make but that others didn’t want to defend.

And defend it I did: on conference calls, in televised briefings, and in long conversations with reporters. I fought with lawyers to get clearance to say that Obama had decided to provide “direct military support” to the Syrian opposition, as we were in the impossible position of not being able to discuss details about a key element of our policy. Legally, we couldn’t say what the support was; all I could say were things like: “This is going to be different—in both scope and scale—in terms of what we are providing to the opposition.” I was giving partial answers about an incremental response and felt as though whatever stockpile of credibility I had built up over four years was being drawn down.

Yet I was also wrestling with my own creeping suspicion that Obama was right in his reluctance to intervene militarily in Syria. Maybe we couldn’t do much to direct events inside the Middle East; maybe U.S. military intervention in Syria would only make things worse.

On August 21, 2013, news broke of a catastrophic chemical-weapons attack in Syria; within a matter of days, the intelligence community had a “high confidence assessment” that a sarin gas attack had killed more than a thousand people in a suburb of Damascus, and that the Assad regime was responsible. There were harrowing accounts of how scores of people had been killed by clouds of gas on the outskirts of Damascus.

A couple of days later, I joined a National Security Council meeting where officials advised Obama, one after another, to order a military strike. This included the chairman of the Joint Chiefs of Staff, Marty Dempsey. Up to this point, he had argued that Syria was a slippery slope where there was little chance of success. Now he said that something needed to be done even if we didn’t know what would happen after we took action.

Obama asked about the UN investigators who were going to the scene of the attack to obtain samples. Could something be done to get them out? The tone of the whole meeting suggested an imminent strike. The adviser who urged the most caution against military action was Chief of Staff Denis McDonough, who raised questions about the legal basis for it and what would come next. What if we bombed Syria and Assad responded by using more of his chemical weapons? Would we put in ground troops to secure those stockpiles? At the end of the meeting, Obama said he hadn’t yet made a decision but wanted military options prepared.