What We Know and Don’t Know About the Missile Attack on Syria

President Trump ordered a barrage of missiles to strike an airfield in Syria on Thursday evening in response to the use of chemical weapons by Bashar al-Assad, the president of Syria. Here are some things we know — and don’t know — about the president’s actions.

What We Know

* Fifty-nine Tomahawk missiles were fired from American destroyers in the eastern Mediterranean at Al Shayrat airfield in Syria, where officials said Mr. Assad’s chemical weapons attack this week originated.

* Mr. Trump ordered the strike after two days of intense deliberations that involved two meetings of his top national security advisers, including one that Mr. Trump conducted from his Mar-a-Lago estate in Florida.

* In announcing the strikes on Thursday evening, Mr. Trump called the chemical attack “very barbaric” and said his decision would “prevent and deter the spread and use of deadly chemical weapons.”

* Administration officials described the missile strikes as a message to the world about Mr. Trump’s resolve and his commitment that the United States will no longer “turn away, turn a blind eye.”

* The Russian military, which is active in Syria, was notified of the strikes in advance, though American officials did not personally inform President Vladimir V. Putin. In a briefing, Secretary of State Rex W. Tillerson criticized Moscow for failing to live up to its promise in 2013 to destroy all of Syria’s chemical weapons, calling Russia either “complicit” or “incompetent.”

What We Don’t Know

* The strike’s impact on the airfield’s capabilities. H. R. McMaster, the president’s national security adviser, said Mr. Assad would “maintain a certain capacity beyond this particular airfield” to use chemical weapons.

* Officials did not provide details about casualties at the airfield, either among Syrians or among others, including Russians, who might have been there when the missiles struck their targets. Officials said measures had been taken to minimize casualties among “third-country nationals.”

* American officials did not publicly address the potential reaction from Mr. Assad or his allies in Russia and Iran.

* It is hard to know whether Mr. Trump’s use of military force this early in his term is an indication that he intends to develop an aggressive foreign policy based on the frequent use of force — something he often criticized as a candidate.

* The political impact of the strikes. Presidents often see a quick improvement in their favorability ratings after using military force. But Mr. Trump acted without the consent of Congress, and in the long term, the public may turn against a president for using the military in this way.