How Many Fighters Does the Islamic State Really Have?

Estimates of the number of fighters in the ranks of the Islamic State in Iraq and the Levant (ISIL) are extraordinarily wide-ranging. On the low end of things, CNN’s Barbara Starr recently reported that “U.S. intelligence estimates that ISIL has a total force of somewhere between 9,000 to 18,000 fighters.” In late 2014, the CIA’s...