Updated at 3:01 p.m. ET

During the presidential campaign, Donald Trump was careful to point out that he thought fighting Syrian President Bashar al-Assad and the Islamic State at the same time was “madness and idiocy.”

I think that our far bigger problem than Assad is ISIS, I’ve always felt that,” he told The New York Times in March 2016. “Assad is, you know, I’m not saying Assad is a good man, ’cause he’s not, but our far greater problem is not Assad, it’s ISIS.”

It’s remarks like that prompted Assad to label Trump “a natural ally.” As recently as last week, things looked good for the Syrian leader when Rex Tillerson, the U.S. secretary of state who serves as America’s top diplomat, said Assad’s future “will be decided by the Syrian people”—comments echoed by Nikki Haley, the U.S. ambassador to the UN, who said: “Our priority is no longer to sit and focus on getting Assad out.” Whether that emboldened Assad, a man whose forces have targeted not just rebels opposed to his rule, but civilians in areas held by the opposition, is unknown. What is known is that on Tuesday a chemical attack in Khan Shaykhun, in rebel-held Idlib province, killed at least 70 people (though some estimates say more than 100 people were killed). Rebels, monitoring groups, U.S., and U.K. officials all blamed the Assad regime for the attack. Syria denied that charge, and Russia, Assad’s main backer in the more than six-year-long civil war, said Syrian aircraft had struck a rebel facility where chemical weapons were being manufactured.

The reaction from the Trump administration sounded markedly different from its earlier acceptance of Assad.

“It’s very, very possible, and, I will tell you, it’s already happened, that my attitude toward Syria and Assad has changed very much,” he said at a joint news conference with Jordan’s King Abdullah. Trump took the opportunity to criticize his predecessor’s policy on Syria, saying President Obama’s  decision not to take military action after drawing a “red line in the sand” emboldened not only Assad, but other actors around the world. Trump said this latest attack in Syria “crosses many, many lines.”

Earlier in the day, Haley urged the UN Security Council to act against Syria: “When the UN consistently fails in its duty to act collectively, there are times in the life of states that we are compelled to take our own action.”   

On Thursday, Tillerson joined in, saying of Assad: “It would seem there would be no role for him to govern the Syrian people.”

Trump, as he often does when pressed on operational specifics, didn’t specify what exactly his administration would do in response to the chemical attack, saying only: “Well, one of the things I think you’ve noticed about me is, militarily, I don’t like to say where I’m going and what I doing.”

As ever with this administration, it’s hard to say what this will mean in practice. The president’s words have so far been vague enough to suggest some sort of action without specifying whether it would necessarily involve the military. CNN reported Thursday that Trump told some congressional lawmakers he was considering military action. But BuzzFeed’s Nancy Youssef reported that the Pentagon was left confused by the president’s remarks.

She wrote: “[T]hree defense officials told BuzzFeed News they cannot begin to craft a military response, if that is what Trump wants, without a clear understanding of what the president wants to see happen in Syria. Does he only want the Assad regime to stop using chemical weapons? Does he want regime change? Is he seeking a negotiated settlement? Or were Trump’s comments simply rhetoric?”

U.S. options in Syria—both military and not—are limited, as well. There’s no public appetite for a long-term U.S. military commitment like the one in Iraq. Other more limited options—like striking Syrian military installations—would have limited impact, primarily because any setback could invite retaliation from Assad’s Russian patrons. Assad has shown he can withstand international sanctions, even if his people cannot. U.S. and Russian efforts to take away and destroy his chemical weapons appear to have failed. These were realities faced by the Obama administration with its Syria policy in the aftermath of deadly chemical weapons attacks, hundreds of thousands of civilian deaths, and a refugee crisis whose political impact has been felt far beyond the Arab and Muslim worlds.

Trump at one time had supported Obama’s military inaction, but on Wednesday he said: “When you kill innocent children, innocent babies—babies, little babies—with a chemical gas that is so lethal—people were shocked to hear what gas it was—that crosses many, many lines, beyond a red line.”

What the consequences of crossing those lines are—or whether there will be any—will become apparent to Assad soon.