Some Americans who joined ISIS have returned to U.S., officials say - NY Daily News
Note that they estimate about 100, and without a functioning government of note backing them.
I don't disagree on that potential for them, and I hope an air campaign will be sufficient to prevent that potential from being realized. It will be necessary to retake the Iraqi territory and hold it with ground troops however. Exactly where those troops will come from remains to be seen. I am honestly pleased the president stepped up and recognized the threat, however reluctantly. On the other hand, I will not endorse something that looks a lot like endless, low level war and all the restrictions that come with it.All this aside, the quasi State status that ISIS enjoys allows them to recruit, screen and train fighters by the thousands- not in groups of say 3-30. This gives them a far larger "talent" pool and a far greater ability to identify dedicated, intelligent recruits and then match them to demanding missions (9-11).