Last November, a few days before the U.S. Presidential election, I was among a group of American reporters and researchers who visited Damascus, Syria, to interview President Bashar al-Assad and his foreign minister, Walid Muallem. At a meeting with the group, Muallem was asked which candidate he favored, Donald Trump or Hillary Clinton.

“I hope they will not elect anybody,” he said.

Muallem laughed at his own joke. He wasn’t serious. Both Muallem and his boss very much wanted Trump to win, hoping that, if he did, some of the pressure on their regime, which has been ostracized around the globe for committing war crimes, would ease up. Assad and Muallem had every reason to think that Trump would give them a more sympathetic hearing than they’d receive from a Clinton Administration. During the campaign, while Clinton was promising to get tough on Assad, Trump had praised him, if for no other reason than that he was battling the Islamic State. Trump had also made numerous positive references to Vladimir Putin, Russia’s leader and Assad’s most important international ally. There was talk, after Trump’s election, of a possible rapprochement with Syria, perhaps facilitated by Putin. And, indeed, the Washington Post reported on Monday that, earlier this year, the Blackwater founder Erik Prince met secretly in the Seychelles with a confidant of Putin to discuss, among other things, a possible deal on Syria.

“I don’t like Assad at all,’’ Trump said in a Presidential debate in October. “But Assad is killing ISIS. Russia is killing ISIS and Iran is killing ISIS.”

The trouble, of course, was that while Assad may indeed have been killing ISIS, he was also killing Syrian civilians—and so prolifically that most Western governments, including the United States, long ago severed diplomatic relations with Assad’s government and called on Assad to step down. Most notoriously, in 2013, the Assad regime was accused by Western governments of using poison gas in the Damascus suburb of East Ghouta, an attack that killed at least fourteen hundred people and wounded more than three thousand, most of them civilians. And though President Barack Obama had previously publicly drawn a “red line” over the use of chemical weapons in Syria, and threatened to respond militarily if it were crossed, he decided, at the last moment, to refrain from any military action, securing instead a promise from Assad to turn over the country’s chemical weapons. It was one of the most significant moments of Obama’s Presidency, and one that Trump and other Republicans ridiculed.

Now comes the moment of truth for President Trump. Sources inside Syria are reporting that a sarin-gas attack in Idlib Province killed dozens of civilians and injured hundreds more on Tuesday. In a statement, Trump blamed Assad’s regime, called the attack “reprehensible,” and said that it “cannot be ignored by the civilized world.” He also described the attack as a “consequence of the past Administration’s weakness and irresolution.”

What happens now? Trump’s comment put forward no clear policy or planned response. During a press briefing on Tuesday, Sean Spicer, the White House press secretary, strongly suggested that the Administration is preparing a military response in order to punish the Syrian government and deter it from carrying out any more chemical-weapons attacks.

The Obama Administration took plenty of actions against the Assad government, including sending arms to rebel groups. But Obama’s other aim, in addition to destroying ISIS, was to avoid a collapse of the Syrian state—the kind that might happen if the United States were to directly attack the Assad regime. Obama feared that the ensuing vacuum in Damascus would be filled by the likes of ISIS and the Al Qaeda affiliate Jabhat al-Nusra. When Obama looked at Damascus in 2013, he saw Baghdad in 2003.

Those were legitimate concerns. As Trump and his advisers go through the options for a potential military strike, they will no doubt be thinking the same thing: If Assad falls, what comes after?