Donald Trump is president; he now bears full responsibility for addressing the tragedy in Syria, and for the consequences of the response he has chosen. But that doesn’t mean we shouldn’t reflect on America’s response to the Assad regime’s previous chemical weapons attacks—for how we interpret the difficult and debatable choice the Obama administration (in which I served) made not to use military force when Assad last used nerve gas against his people will shape our thinking about this and similar crises for a long time to come. The lesson I would draw from that experience is that when dealing with mass killing by unconventional or conventional means, deterrence is more effective than disarmament.

After Assad’s horrific 2013 sarin gas attack on civilians, President Obama settled first on deterrence—threatening a punitive military response—then changed course when Assad agreed to disclose and surrender his chemical weapons. There were many reasons for Obama’s decision to forego military action, from his own concerns about the risks of getting involved in Syria’s war to the shameful refusal of most members of Congress to back him up. In any case, the administration and many outside observers argued then that the U.S. had achieved a better outcome by threatening force and then negotiating a deal than if we had actually used force. Air and cruise missile strikes could not have eliminated Assad’s chemical weapons arsenal, but the diplomatic deal, proponents argued, did.

That argument was never persuasive to Syrians being killed by the barrel bombs and rockets that the chemical weapons deal allowed Assad to keep using. But even if one accepts that there is something uniquely awful about poison gas, the Syrian regime’s repeated use of chlorine weapons after 2013, and now its apparent reuse of sarin, shows the difficulty of relying on disarmament alone to stop a dictator from killing by all means at his disposal. No disarmament regime is foolproof, and it was always understood that Assad likely hid some elements of his chemical weapons production capacity from inspectors. A state that calculates that using a weapon or tactic of war is in its interest will generally find a way to do so.

The more effective strategy is to establish that the costs of using such a weapon or tactic will outweigh its benefits, even if a state keeps the capacity to do so. It is deterrence that has prevented the use of nuclear weapons by all states that possess them since 1945. Efforts to stop proliferation of banned weapons and to disarm states that maintain them should of course also continue. But enforcing the norm against their use is more important. This is what was at stake after Assad launched his deadly gas attack in 2013—not merely American credibility following Obama’s comments about the use of chemical weapons crossing a “red line” (I agree with those who say the U.S. should not go to war for that reason alone), but to affirm that the norm against killing by chemical weapons cannot be violated without the perpetrator suffering the most serious consequences. (An analogy: I support tougher gun control in the U.S., but gun control without enforcement of criminal laws against murder would be absurd.)

The better approach following Assad’s chemical attacks in 2013 would have been to launch both punitive and preventive strikes against his military, trying to eliminate as many as possible of the aircraft that could be used to deliver chemical weapons, followed by the imposition of a no-fly zone to keep the remainder of his air force grounded, and a threat to strike again should he use ground-based weapons to launch chemical strikes in the future. This is more than what was likely in the offing, but would have been militarily feasible. Stand-off weapons such as cruise missiles could have destroyed a significant number of Syria’s fighter jets and helicopters on airfields with no risk to American service members and little risk of civilian casualties (since military hangars and runways are not close to residential buildings).

As for a no-fly zone, the U.S. military enforced one against the Saddam Hussein regime in northern Iraq for over a decade with spectacular humanitarian benefits; in Syria, regime planes flying over most of the country’s cities would have been in range of American aircraft patrolling even outside Syrian airspace. This is what Assad feared the U.S. would do after that first massive sarin attack; while the administration was considering strikes, he essentially stopped his military operations throughout the country. Had the administration gone forward, it still could have pursued a disarmament deal (since Assad would have been desperate to get us to stop our strikes), while launching a broader diplomatic push to diminish the violence in Syria.

President Obama argued, at this and all other points when military intervention in Syria was considered, that military action would draw America into Syria’s intractable civil war without, by itself, solving it, and that such action always brings unintended consequences. I think he was 100 percent right to fear these things. Proponents of intervention too often overstated their case. We could not have gotten rid of Assad or ended the war in Syria by bombing a few of his military installations or imposing a no fly zone. Nor will we do so now. With the added leverage military action would have given him, it is possible that Secretary of State Kerry could have negotiated some kind of political settlement—the longer I worked for him, the more admired his passion and persistence in pursuit of that goal. But given the nature of the Assad regime (a totalitarian police state unlikely to give up power whatever it promised in Geneva) and the chaotic complexity of the rebellion against it, I still think the effort would likely have failed even had America used force.

But a military effort along the lines I lay out above could have achieved other, more limited, but still worthwhile goals: It would have reinforced the prohibition against chemical weapons and ensured that Assad would not use them again. It would have created areas in Syria that would be safe from the regime’s devastating air strikes, enabling, if not a political settlement, then at least a more durable cease-fire, resulting in less killing and suffering, and preventing the mass exodus of refugees from Syria (which mostly took place after 2013). That, in turn, could have diminished the fear-mongering and populist backlash that transformed the politics of Europe once the refugees started arriving there (it is reasonable, for example, to suggest that absent the Syrian refugee crisis, there might not have been a Brexit).

Under these circumstances, Syrians also would have had less reason to turn to the best-armed extremist groups for protection against the regime, and ISIS would have had a harder time exploiting their insecurity to gain a foothold (keep in mind that Raqqa didn’t completely fall to ISIS until 2014). The U.S. would have had an easier time forging partnerships with Syrians in opposition areas—both moderate armed groups and local civil society—to push back against ISIS and al-Qaeda, which they could not effectively do while simultaneously being slaughtered by the regime. Perhaps some of the incalculable harm ISIS has since inflicted—the lives it has taken and insecurity it has created in Europe and the United States—might have been avoided.

It is essential to acknowledge that, had the administration done all this, the results would still have been deeply unsatisfying. American aircraft would likely be patrolling a no-fly zone with no end in sight. Meanwhile, on the ground, violence between the regime and opposition would likely continue in some parts of Syria. There would still be terrorist groups in the country. The conventional wisdom in Washington would be that Obama got suckered into another one of the messy military adventures in the Middle East he said he wanted to avoid. No one would credit him for preventing the world-changing catastrophe that Syria has become, because it likely wouldn’t have happened and thus would not have been imagined.

This, unfortunately, is what responsible global leadership sometimes demands. There are norms that preserve some equilibrium between chaos and stability in the world; that keep sociopaths like Assad from undermining that equilibrium, and the sense of security without which the freedoms we enjoy cannot exist. Someone has to enforce those norms, and as much as we would like an ever-ready coalition of friendly allies or the United Nations to bear that burden (a worthy and still not impossible dream), there are still times when only America can do the job. President Obama recognized the Russian invasion of Ukraine as a threat to fundamental norms, and mobilized the international community against it (for which he deserves far more credit than he’s gotten). The crisis in Syria, from the use of weapons of mass destruction against civilians, to Russia’s eventual destructive intervention, was equally a threat to norms that keep the world civilized and safe.

Since 2013, millions of Syrians have fled their country; terrorists based in Syria have unleashed carnage around the world and confidence in democratic institutions has frayed from Europe to the United States, as it always does when people feel insecure. And now America is bombing Syria every day anyway, while putting more and more troops on the ground (something no proponent of intervention advocated in 2013), just to deal with ISIS—a necessary effort, but one that will do nothing to solve underlying problem. In fact, the subordination of all other aims in Syria to the fight against terrorism makes the underlying problem harder to solve.

The problem is more complicated today than it was in 2013. The best possible outcome of any American intervention will be even less satisfying than it could have been then. But military action to reestablish the prohibition against gassing civilians is still the right thing to do, and Trump was right to do it quickly. The question is whether, having chosen that path, he is capable of following up punitive strikes with a real effort to protect Syrians from all forms of mass violence, and to make ending the war, not just counterterrorism, his priority in Syria. Will there be further strikes targeting Assad’s capacity to kill by conventional as well as chemical means, for example? Will the administration insist on a general ceasefire and an end to the regime’s blockades of humanitarian aid and back it up with at least an implied threat of further military involvement?  Will it reengage with what’s left of Syrian civil society, fund humanitarian aid, and resume the generosity we once tried to show Syrian refugees? I have no confidence that Trump has the desire or attention span to do these things, given the dysfunction within his administration, the incoherence of his policies thus far, and his strange entanglement with Russia. But he will deserve credit if he does.


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