Marines and sailors from 1st Battalion, 10th Marines have deployed in support of operations in Iraq and Syria, Corps officials announced on Friday.

Their main mission will be to help Syrian Arab and Kurdish forces that are fighting the Islamic State group, a military official said.

They will replace previously deployed Marines who were providing “critical fire support to Coalition and local partnered forces,” according to II Marine Expeditionary Force.

Officials refused to say Friday how many Marines and sailors are part of this deployment. The battalion is based at Camp Lejeune, North Carolina.

Marine Corps artillery in Syria has been supporting a coalition of Syrian Kurdish and Arab fighters, who are in a tough battle to drive the Islamic State group out of its de facto capital of Raqqa, Syria.