STEVE INSKEEP, HOST:
Let's recall the size of the enemy the United States wants to confront. There are conflicting estimates of how many troops ISIS can field. No estimate depicts the group as especially large. In the past, the CIA estimated the group included about 10,000 militants. Its success capturing territory inside Iraq and Syria and then the propaganda advance of declaring a caliphate has attracted new recruits. The new CIA estimate is not so precise, but it's a lot bigger - 20,000 to 31,000 fighters. Transcript provided by NPR, Copyright NPR.