The U.S.-led effort to fight the Islamic State in northeastern Syria since 2014 has been as controversial and poorly understood as it has been significant. Advocates of fighting by, with and through the Kurdish-led Syrian Democratic Forces (SDF) view the campaign as a near-ideal case study of a cost-effective U.S. military intervention that should be duplicated in the future. Critics of the campaign say that the U.S. allied itself with a terrorist group and endangered its ties with Turkey, a long-stranding NATO partner; losing sight of strategic priorities in order to win tactical victories at low cost. This book combines general research with 50 interviews gathered in Syria with Kurdish, Arab and Christian SDF officers, and 50 interviews with U.S. and French officials and military officers with on-the-ground involvement in the war. It provides an unprecedented window into how the war was really prosecuted, in the eyes of the participants at all levels, uniquely looking not only at how U.S. soldiers view their partner forces, but how the local partners view them in return. This is a unique and essential insight into US strategy in Syria and beyond.