American forces engaged Pro-Assad troops with artillery, rockets and air strikes on Tuesday following what CENTCOM has characterized as an “unprovoked attack” against U.S. backed forces in Syria. According to a statement released by Operation Inherent Resolve, American advisers were present at the time of the attack, though none were injured or killed.

“Syrian pro-regime forces initiated an unprovoked attack against well-established Syrian Democratic Forces headquarters Feb. 7,” the statement reads. “Coalition service members in an advise, assist, and accompany capacity were co-located with SDF partners during the attack eight kilometers east of the agreed-upon Euphrates River de-confliction line.”

According to the Syrian Observatory for Human Rights, the Syrian military’s attack against the Syrian Democratic Forces (SDF) headquarters killed 21 and injured 125, prompting a response from American assets in the region.

“In defense of Coalition and partner forces, the Coalition conducted strikes against attacking forces to repel the act of aggression against partners engaged in the Global Coalition’s defeat-Daesh mission.” The CENTCOM release said.