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 would consider the principal threats to start with Russia. And it would certainly include any nations that are looking to intimidate nations around their periphery, regional nations nearby them, whether it be with weapons of mass destruction or I would call it unusual, unorthodox means of intimidating them.

In a country with millions of people & cars going everywhere, the enemy is going to get a car bomb out there once in a while.

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.

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.

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 polite, be professional, but have a plan to kill everyone you meet.