When you had thugs and bullies and killers imposing their will on their own people or other people - if you don't respond to it, it just keeps coming because they're encouraged by their own success.

There are very few fighters in the ISIS organization in Iraq and Syria coming from the United States; most of them have either come from a region of the Middle East or from Europe.

Duty' is a refreshingly honest memoir and a moving one. Mr. Gates scrupulously identifies his flaws and mistakes: He waited too long, for example, for the military bureaucracy to fix critical supply issues like the drones needed in Iraq and took three years to replace a dysfunctional command structure in Afghanistan.

The homegrown terrorists are the most significant because any fighter returning from Syria to the United States would likely be identified and detected by our intelligence and law enforcement agencies.