Islamic State (IS) is a transnational insurgency group-animated by radical Sunni Islamic ideology relying heavily on the use of terrorism-that since 2013 has fought to occupy a substantial amount of territory in both Iraq and Syria. As of late 2014, IS controlled approximately 30 percent of Syrian territory containing 2-3.5 million people. It begrudgingly shares with Kurds and other opposition groups-some sectarian and some secular-the approximately 45 percent of Syrian territory that the Syrian government has unwillingly relinquished to rebel forces. The majority of the territory held by IS in Syria is desert, and is concentrated in the northeastern and eastern provinces. However, it has control over water and energy resources from which it derives significant influence and revenue.