President Trump on Saturday vowed to retaliate against ISIS, after three Americans — two U.S. soldiers and their interpreter — were killed in an attack in Palmyra in central Syria. They are the first U.S. casualties in Syria since Syrian rebels toppled the regime of Bashar al-Assad a year ago. According to the Pentagon, the attack comes as the U.S. was reducing its troops in the country from 2,000 at the beginning of the year to around 1,000 today.