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.

I think the core problem is much closer to recognizing where force is of value, where it is useful, and to distinguish that from situations in which war is not useful or is indeed counterproductive.

With respect to the outlines of what's in the Army Field Manual, there's no doubt in my mind about the limitations it places not only on the DOD, but on the Central Intelligence Agency. And I'll always comply with the law.

The first time you blow someone away is not an insignificant event.

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 face now an era where we're going to be fighting the terrorist threat. I mean, that's simply a reality we are going to have to address that one.

We have the most skillful, firecest, and certainly the most ethical ground forces in the world... I'm not saying we have to commit right now, but certainly don't pull it off the table.