You are part of the world's most feared and trusted force. Engage your brain before you engage your weapon.

Anyone who kills women and children is not devout. ISIS cannot dress themselves up in false religious garb and say that somehow this message has dignity. We're going to strip them of any kind of legitimacy.

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.

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.

What would you do differently as defense secretary to compensate for this record in which the greatest military in the world, as we are constantly told, doesn't get the job done?

The destruction that we have wreaked in the various theaters in which we've been engaged is really quite astonishing. But again, lethality, destruction, killing doesn't seem to achieve our objectives. So, my own sense is that a lack of lethality does not define the core problem.

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