On the foreign policy side, there's the risk of being too spontaneous and too disruptive where you end up doing more harm than damage. And figuring out that balance is where having strong people around you matters.

Defense is not like other discretionary spending.

If Iraq and Afghanistan have taught us anything in recent history, it is the unpredictability of war and that these things are easier to get into than to get out of, and, frankly, the facile way in which too many people talk about, 'Well, let's just go attack them.

I've seen, all too often in my career, people coming in to lead agencies and organizations and trying to impose change from the top down. Never works. You never have enough time.

Development is a lot cheaper than sending soldiers.

If possible, to be in a position to announce who is going to step in as the interim immediately. And if possible, to announce who you're going to nominate to replace that person. For that to be somebody of impeccable integrity and reputation disarms a lot of the worst criticism that it's some kind of a power play. It's a professional approach to replacing a senior official, which is always going to get a lot of attention.

I think that - that the disruptive nature, the tough talk on North Korea, the military deployments, sending the missile defense system to South Korea, I think these are all good things to have done.