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

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.

Since 9/11 we've been engaged in wars around the world, and General [James] Mattis has been a leading battlefield commander in many of those theaters, including in the April 2004 siege of Fallujah, where the US Marines killed so many people that the municipal soccer stadium in the city had to be turned into a graveyard for the dead.

I was struck by the fact that none of the senators, basically, asked General [James] Mattis, "Well, General, how is it that we haven't won?" We haven't won anywhere, 'winning' in the sense of conclusively achieving our political objectives, however you might want to define those objectives.

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.

No war is over until the enemy says it's over. We may think it over, we may declare it over, but in fact, the enemy gets a vote.

Nothing keeps me awake at night. I keep other people awake at night.