We must be honest in acknowledging that neither Germany nor the US has the luxury of assuming that we can skate by on half-measures in Afghanistan and Pakistan and not risk suffering the consequences.

I'm apologetic when I feel like I've made a mistake. And when I have done a disservice to myself or someone else. But I don't feel a need to apologize for doing or saying something that I think needs to be said, just because it may not sit comfortably with somebody else.

I have been to Libya and walked the streets of Benghazi myself.

It is manifestly in the interest of the United States to deal with the very real threat that climate change poses. And that's why President Obama has worked so hard to reduce our own emissions and to lead internationally in forging the Paris climate agreement.

President Obama is funny, he's thoughtful, he's challenging, he's fun to work with - and it's been an extraordinary privilege.

For the United States to recommit itself to the obligation that we undertook in the Nuclear Non-Proliferation Treaty that many other states undertook, which was to work towards disarmament and the eventual elimination of nuclear weapons, is something that manifestly serves our national security interests.

Peace, prosperity, and democracy cannot endure if imposed from the outside. We should cease to make false distinctions between peacekeeping and prevention; they are in fact inextricably linked.