US troops sit atop an armoured vehicle on a road near the northern Syrian village of Ain Issa on June 3, 2017. Naumann said, "We have around a thousand US forces that are operating throughout Northeast Syria to execute our defeat Daesh and security mechanism zone missions." US and Turkish military forces have conducted a series of helicopter surveillance flights over the area and have conducted one ground patrol as part of the arrangement. "We're pretty convinced that as we work with Turkey, the idea of a Turkish incursion into Syria has gone down substantially," Maier added. In December, President Donald Trump announced that he would withdraw all US troops from Syria, an announcement that sparked the resignation of then-Defense Secretary James Mattis.