I will always be an advocate in terms of wars of necessity. I am just much more cautious on wars of choice.

I wish I could set deadlines for the Congress, but that's just not the way the Constitution is written.

I think that Vladimir Putin is certainly getting a lot of publicity for what the Russians are doing. And I'm not sure that's unwelcome to him. I think this is a guy who saw the U.S. basically come out against him in his reelection campaign in 2012. He saw the U.S. being behind all of the color revolutions in Eastern Europe and in Georgia and Ukraine and so on. So his view is the West has been interfering in his politics for years.

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

There will be boots on the ground if there's to be any hope of success in the strategy.

We should never lose sight of the ethos that has made the Marine Corps - where 'every Marine is a rifleman' - one of America's cherished institutions and one of the world's most feared and respected fighting forces

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.