In 2013, Assad escaped punitive strikes by the United States by agreeing to a Russian-brokered deal that was supposed to remove his chemical munitions and block his ability to reconstitute a chemical-warfare capability. It did not do so, and nearly four years later Assad—perhaps led to believe by Trump’s remarks on the campaign trail that U.S. forces would not remain in Syria for long—returned to the use of sarin. No doubt he was shocked by the quick and lethal response.
Shock, however, did not translate into paralysis. With the support of Russia and Iran, Assad calculated that he could persist with his political survival strategy—mass homicide—and even employ chemical weapons for terror effects provided he stopped short of using sarin, which is banned under the 1993 Chemical Weapons Convention. Assad's addiction to chemicals was far from cured: His use of chlorine gas canisters (often packed in barrel bombs) never ceased. But he calculated that sarin was the specific red line not to be crossed.
This calculation was not a hunch. Assad was able, with the help of Vladimir Putin, the president of Russia, to deduce soon after the cruise-missile strike of April 2017 that it was a one-time gesture—that, provided he stopped short of using sarin, any other acts of mass murder or state terror would draw no U.S. response beyond the customary hand-wringing in the United Nations Security Council.
What the Trump administration failed to do in April 2017 was deliver the following message to the Kremlin: You need to get your client out of the business of mass homicide. If he persists, we will exact prices at times and in places of our choosing. This is not just about chemicals. It is about what your client is doing to our friends, our allies, and to us by providing recruiting fodder for Islamist extremists around the globe. Perhaps that’s the message intended by Trump’s warning of imminent action.
Absent such a message, Assad saw the red line on sarin as a green light to do everything else. On the chemical front, he continued his promiscuous use of weaponized chlorine, as he had done during the Obama years. And when he heard Trump speak publicly about his desire to get out of Syria quickly, he may have concluded that he could again indulge his addiction to the stronger stuff.
As he did a year ago, however, Assad may have miscalculated. Trump’s call to pull troops out of Syria notwithstanding, administration officials—long before the latest incident—were troubled and perplexed by the breakdown of deterrence they thought they had purchased with the April 2017 retaliatory strike. H.R. McMaster, the recently replaced national-security adviser, spoke publicly about that failure during the February 2018 Munich Security Conference.
Now the president and John Bolton, his new national-security adviser, face the possibility that Assad, a crime family chieftain, has again placed American credibility on the line. Based on the latest reports, the Pentagon has likely prepared a menu of regime targets from which to select. Can any good come from a decision to strike?