The U.S. military operation in Syria and Iraq says it is sending home more the 400 Marines and their artillery from Syria, after they accomplished their mission against the Daesh terror group.

The press unit for Operation Inherent Resolve says the 1st Battalion, 10th Marine Regiment was supporting local partner forces with artillery firepower to defeat Daesh militants in their former capital city, Raqqa.

The city fell to a mix of Kurdish, Arab and other local forces on Oct. 20 after a 4-month assault that was backed by U.S. and international coalition airpower and artillery.

"With the city liberated and ISIS on the run, the unit has been ordered home. Its replacements have been called off," the unit announced in a statement Thursday, using an alternate acronym for Daesh.

The U.S. is estimated to have more than 1,500 troops posted to Syria, including special forces, forward air controllers, and at least one Marine artillery unit. They have more than a dozen bases in north Syria.