Chuck Hagel: “I was wrong.”

American military power alone cannot and will not eradicate the threats posed by ISIL to the United States, our allies, and our friends and partners in the region.

This is so unpredictable. And we've never seen anything quite like this in our lifetime, so there is no playbook here.

They're not trained for law enforcement.

There's a perception that it is the military's responsibility to fix the problem. Problems are not fixed by militaries.