The operation, which the Trump administration authorized in retaliation for a chemical attack killing scores of civilians this week, dramatically expands U.S. military involvement in Syria and exposes the United States to heightened risk of direct confrontation with Russia and Iran, both backing Assad in his attempt to crush his opposition.
The attack may put hundreds of American troops now stationed in Syria in greater danger.
They are advising local forces in advance of a major assault on the Syrian city of Raqqa, the Islamic State’s de facto capital.
The decision to strike follows 48 hours of intense deliberations by U.S. officials, and represents a significant break with the previous administration’s reluctance to wade militarily into the Syrian civil war and shift any focus from the campaign against the Islamic State.
Senior White House officials met on the issue of Syria Wednesday evening in a session that lasted into early Thursday, and Defense Secretary Jim Mattis, Secretary of State Rex Tillerson and Army Lt. Gen. H.R. McMaster, the national security adviser, have communicated repeatedly since Tuesday’s chemical attack, the officials said.