On Sunday, Obama notified Congress of the air strikes. “The failure of the Mosul Dam could threaten the lives of large numbers of civilians, endanger U.S. personnel and facilities, including the U.S. Embassy in Baghdad, and prevent the Iraqi government from providing critical services,” Obama said in a letter to Congress. According to the U.S. military, the strikes on Sunday near the Mosul Dam destroyed three ISIS armed vehicles, an ISIS vehicle-mounted anti-aircraft artillery gun, an ISIS checkpoint and an IED emplacement.

The Kurdish forces, known as peshmerga, launched the operation early Sunday to retake the Mosul Dam, Gen. Tawfik Desty, a Kurdish commander, told The Associated Press. He said his forces now control the eastern part of the dam and that fighting is still underway.

Another commander said Kurdish forces later were hindered by roadside bombs planted by retreating Islamic State fighters. He added that peshmerga forces had taken the nearby town of Tel Kasouf by Sunday morning.