Once ISIS is defeated, there is a larger effort under way to make certain that we don't just sprout a new enemy. We know ISIS is going to go down. We have had success on the battlefield. We have freed millions of people from being under their control.

Treachery has existed as long as there's been warfare, and there's always been a few people that you couldn't trust.

General [James] Mattis's primary experience - indeed, his only experience - is as a member of the United States Marine Corps, where he served for 41 years. That's his experience.

We have the most skillful, firecest, and certainly the most ethical ground forces in the world... I'm not saying we have to commit right now, but certainly don't pull it off the table.

What concerned me was that [James Mattis] played not only a critical role as a battlefield commander in Fallujah, but also, afterwards, when he was promoted to various other higher-ranking positions, he served as a convening authority in court-martial proceedings against various marines who had been accused of atrocities - for example, in the Haditha massacre, where a group of marines went on a killing spree after one in their unit was killed.

Be the hunter, not the hunted: Never allow your unit to be caught with its guard down.

Anyone who kills women and children is not devout. ISIS cannot dress themselves up in false religious garb and say that somehow this message has dignity. We're going to strip them of any kind of legitimacy.