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

ISIS is a threat to all civilized nations. America's intention is that the foreign fighters do not survive the fight to return home to North Africa, to Europe, to America, to Asia, to Africa. We're not going to allow them to do so. We're going to stop them there and take apart the caliphate.

Right now, Russia's future should be wedded to Europe. Why they see NATO as a threat is beyond me. Clearly, NATO is not a threat.

I just hope we can find our way back to engaging with one another, arguing strongly with one another, and then going down and having a root beer together or something and - and having a good laugh about it as we work together for the best interests of the next generation of Americans who are going to inherit this country.

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

You cannot allow any of your people to avoid the brutal facts. If they start living in a dream world, it's going to be bad.

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.