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

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.

There are some people who think you have to hate them in order to shoot them. I don't think you do. It's just business.

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.

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.

I can't imagine that I would be asked that by the president-elect [Donald Trump], or then-president [Barack Obama]. But it's - I'm very clear. I voted for the change that put the Army Field Manual in place as a member of Congress. I understand that law very, very quickly and am also deeply aware that any changes to that will come through Congress and the president.

When you're in operations, the best thing you can do at the top level is get the strategy right. You have to get the big ideas right, you have to determine what is the policy, what is the level of effort you're willing to commit to it? And then you delegate to those who have to execute that strategy to the appropriate level. What's the appropriate level? It's the level where people are trained and equipped to take decisions so we move swiftly against the enemy.