No president is well-served by groupthink or by everybody singing from the same sheet of music they think he's on.

I think in the context of senior government positions, I think an anecdote of what I told President-Elect Barack Obama when we had our first meeting. And I said, "You don't know me. Can you trust me? Why do you think you can trust me?" and so on. But at the end, I said, "You can count on me to be loyal to you. I will not leak. I will keep my disagreements with you private. And if I cannot be loyal, I'll leave." Loyalty means doing what you think is in the best interest of that person as well as the country.

If there's ever an example that military power alone cannot be successful in Afghanistan, I think it was the Soviet experience.

I think that Vladimir Putin has decided, in a very strategic way, to turn the tables and do everything in his power to, as we've described Russian elections as illegitimate, to try and communicate to the rest of the world that Western elections are illegitimate. And it's not just us, we know that now. It's Germany, it's France, it's a number of other countries.

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.

Well, I've ruffled a few feathers at all the institutions I've led. But I think that's part of leadership.

I had no difficulty as Secretary of Defense moving from the Bush administration to the Obama administration.