WASHINGTON — 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.

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

• The Syrian Army says that the U.S. attack has killed six people.

• 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.”

• 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.

• Russia reacted harshly on Friday, maintaining its view that Mr. Assad had not bombed his people with chemical weapons. Iran, Russia’s main regional ally in buttressing Mr. Assad, also condemned the American attack.