Currently, the total number of ISIS fighters is between 20,000 and 30,000, similar to the levels when the air campaign began, despite thousands of ISIS fighters believed to have been killed in coalition air strikes.
Turkey, the prime transit point into Syria, is still struggling to stem the flow. However, the U.S. believes its agreement to allow U.S. air strikes from a Turkish air base and to help establish a safe zone indicate Istanbul is stepping up.
The administration is also claiming gains on the ground.
"In Iraq, ISIL has lost the freedom to operate in some 30% of the territory that they held last summer," White House spokesman Josh Earnest told reporters Friday, using another name for ISIS. "Overall, ISIL has lost more than 17,000 square kilometers of territory in northern Syria."