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.

We are going to have to continue to keep the pressure on the enemy. There is no room for complacency on this.

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 don't see lethality as the problem. I mean, the lethality of US forces is quite remarkable.

The United States has been essentially engaged in an ongoing war that most people date from 2001. That war has taken us to Afghanistan, to Iraq, in a lesser way to other countries - Libya, Somalia, Yemen.

We can kill lots of people. We do kill lots of people. We can destroy virtually anything we choose to destroy.

The American people and the American military will never get used to civilian casualties. And we will - we will fight against that every way we can possibly bring our intelligence and our tactics to bear. We're not the perfect guys, but we are the good guys.