North Korea is a direct threat to the United States. They have been very clear in their rhetoric we don't have to wait until they have an intercont- intercontinental ballistic missile with a nuclear weapon on it to say that now it's manifested completely.

You are part of the world's most feared and trusted force. Engage your brain before you engage your weapon.

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.

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.

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.

It is mostly a matter of wills. Whose will is going to break first? Ours or the enemy's?

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.