BEIRUT — A U.S.-backed force in Syria announced Tuesday that it was resuming operations against the Islamic State after an earlier push stalled as fighters left for other battlefronts.

The Syrian Democratic Forces (SDF), a Kurdish-dominated alliance backed by the United States, has handed the Islamic State several defeats. The SDF in October ousted the extremist group from Raqqa, the de facto capital of the Islamic State’s self-proclaimed caliphate. But the fight for the militants’ last stronghold, the oil-rich eastern province of Deir al-Zour, foundered this year when thousands of SDF fighters left to battle another foe — Turkey, which seized much of the Kurdish-
dominated Afrin enclave in northern Syria.

The suspension of the Deir al-Zour offensive in March allowed the Islamic State to embed across a swath of desert along Syria’s border with Iraq. Estimates for the number of militants remaining across the two countries range between 1,000 and 3,000.

As the territorial caliphate of the Islamic State nears its end, the Post’s Liz Sly reflects on its rise and ongoing fall and discusses what could come next. (William Neff/The Washington Post)

With Turkey firmly in control of Afrin, the SDF is turning its attention back to battling the Islamic State, which is also known as ISIS. 

“We have rearranged our forces,” Kino Gabriel, a spokesman for the SDF, said on Tuesday.

U.S. Defense Secretary Jim Mattis said last week that he expected a “reenergized” effort against remnants of the Islamic State in eastern Syria. A U.S.-led military coalition has backed the ground operation with airstrikes since June 2014, forcing the Islamic State’s near-defeat but also leveling districts and causing mounting civilian casualties along the way.

The U.S. role in Syria remains uncertain, however, as President Trump pushes for a speedy withdrawal while Mattis and other administration officials encourage a slower drawdown.

In a statement Tuesday, Maj. Gen. James B. Jarrard, commanding general of the U.S.-led fight against the Islamic State, said the coalition would “ensure the liberation of all terrain held by ISIS.”

“This is a key milestone in bringing lasting stability to both Iraq and Syria,” he said.

According to the SDF, Islamic State fighters have stepped up attacks in recent weeks, repeatedly targeting the U.S.-backed force. 

“They are in their last strongholds now, and these contain a big number of jihadis. We know there will be a higher number of suicide attacks, of car bombs and of the explosives that they have planted,” Gabriel said.