Ultimately, if you think about all the youth that everybody has mentioned here in Africa, if everybody is raising living standards to the point where everybody has got a car and everybody has got air conditioning, and everybody has got a big house, well, the planet will boil over - unless we find new ways of producing energy.

The people there, the community, the lessons that I learned -- they're all based right in this few square miles where we'll now be able to give something back and bring the world back home after this incredible journey.

For the world has changed, and we must change with it

We are willing to uphold principles that have resulted in unprecedented prosperity and security throughout Europe and around the world. With the threat of climate change only becoming more urgent, Angela [Merkel] and I focused on the need for American and E.U. leadership to advance global cooperation.

it’s important to make sure that we’re talking with each other in a way that heals, not in a way that wounds." - Barack Obama, 44th U.S. President

We remember the grind of the insurgency -- the roadside bombs, the sniper fire, the suicide attacks. From the 'triangle of death' to the fight for Ramadi; from Mosul in the north to Basra in the south -- your will proved stronger than the terror of those who tried to break it.

When your team loses, everybody gets deflated. And it's hard, and it's challenging.