The United States has become a combatant in Syria’s horrific civil war. The Trump administration, which intervened with deadly military force, gives no sign of knowing what it’s doing or why.

Secretary of State Rex Tillerson has absurdly tried to suggest that nothing has changed. He is wrong. Fifty-nine cruise missiles constitute a policy shift. So what is the administration’s strategic vision? What is its desired outcome? How does it get there? And what happens next?

U.N. Ambassador Nikki Haley said Sunday that the administration cannot envision “a peaceful Syria” with dictator Bashar al-Assad still in power. Tillerson went on a different Sunday show to say that Assad’s fate is up to “the Syrian people.” Neither statement had much grounding in the reality of a heartbreakingly brutal war that has killed about 400,000 people and displaced half of Syria’s population.

Who’s going to make Assad leave? “The Syrian people” have been trying to get rid of him for about six years, yet he remains. The Obama administration believed it had at least negotiated the surrender of Assad’s capacity to use chemical weapons, but last week’s sarin attack demonstrates otherwise. There is no political process through which Syrians can express their will. There is only a grinding, multi-sided conflict that has allowed the Islamic State, also known as ISIS, to seize huge swaths of territory.

“Wouldn’t it be nice if we got together with Russia and knocked the hell out of ISIS?” Donald Trump asked during the campaign. But nice does not equal feasible. Russian President Vladimir Putin has sent military forces to help Assad maintain his grip on power. Working with Russia would require the coldbloodedness to look past Assad’s myriad atrocities — and Trump’s description of the “beautiful babies” who were “cruelly murdered” was hardly the rhetoric of realpolitik.

(Sarah Parnass,Julio Negron/The Washington Post)

Trump seemed willing to try some sort of alliance — but then came the chemical attack. And now, having bombed the Sharyat airfield near Homs from which the planes carrying chemical weapons took off, Trump has sided against Assad in deed if not in word. Careful diplomatic statements cannot disguise the obvious fact that the United States and Russia are working at cross-purposes.

At least in part, Trump seems to have been determined not to follow the example of the Obama administration. In 2012, President Barack Obama declared chemical-weapons use a “red line” that must not be crossed. When Assad crossed it anyway, Obama prepared to strike — but decided at the last minute to ask Congress to give him authorization to use force. The request never received a floor vote in Congress.

Trump enthusiastically supported Obama’s restraint at the time . He warned throughout the campaign against deeper U.S. involvement in Syria. Now his decision to launch the cruise missile strike is being applauded by foreign policy traditionalists of both parties — the establishment figures who gave us the disastrous war in Iraq — as a show of U.S. “strength” and “resolve.” That should worry us all.

Red lines and symbolic displays of force do not constitute a plan. I have long opposed U.S. military intervention in Syria because I did not see how such action — within the parameters of the possible — would make the situation better. I still don’t.

A punitive strike to deter Assad from using chemical weapons does nothing to protect the millions of desperate civilians who remain vulnerable to conventional weapons wielded by the Syrian government, such as deadly barrel bombs. Indeed, Assad reportedly made a point of having warplanes take off from Sharyat on bombing runs soon after the missiles landed; while the base suffered considerable damage, runways were left intact. Civilians are also under attack by Russian forces, the Islamic State and various jihadist and non-jihadist rebel groups.

I have to wonder what Assad hoped to accomplish by using chemical weapons in the first place. Could he have been trying to bait the United States into military action — and thus drive a wedge between Trump and Putin? The Russian strongman is not what you’d call sentimental, and he might abandon Assad if Trump made it worth his while. Such dishonor among thieves now seems less likely, at least in the short term.

If the cruise missile attack was a one-and-done warning, it changes nothing. If it was an opening salvo of some kind, what follows? Either we’re on a slippery slope toward deeper military involvement, or we remain helpless witnesses to unspeakable carnage. Maybe Trump, having acted as commander in chief, feels good about those alternatives. I don’t see why anyone else should.

Read more from Eugene Robinson’s archive, follow him on Twitter or subscribe to his updates on Facebook. You can also join him Tuesdays at 1 p.m. for a live Q&A.