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 can kill lots of people. We do kill lots of people. We can destroy virtually anything we choose to destroy.

If in order to kill the enemy you have to kill an innocent, don't take the shot. Don't create more enemies than you take out by some immoral act.

I'm from the American West. We have forest fires out there. And some of the worst forest fires in our history, the most damage were caused when we pulled the fire crews off the line too early. And so we're going to have to continue to keep the pressure on the enemy - ISIS. There's no room for complacency on this.

We do everything humanly possible, consistent with military necessity, taking many chances to avoid civilian casualties, at all costs.

We do not draw red lines unless we intend to carry them out. We have made very clear that we are willing to work with China, and we believe China has tried to be helpful.

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.