“Officially, there are now 3,650 U.S. troops fighting ISIS in Iraq. The real number of Americans involved in the war is closer to 6,000. In the war against the self-proclaimed Islamic State, there are two ways to count the number of U.S. boots on the ground. There’s the one that officials admit to. Then there’s the ground truth.”

Source: Pentagon Won’t Say How Many Troops Are Fighting ISIS – The Daily Beast