Tensions and violence in cities across America are reminders of how quickly communities can erupt with an absence of social trust.

Trust is an amazing commodity. The Afghan people often talk to me about having to develop trust in America, because they believe that we deserted them in 1990 and 1991.

The reality is when you make 'America First' a bumper sticker and pump it overseas, what you're telling them is 'America Only'.

America needs a big idea that plays to its strength. It should look to national service.

The challenge that we faced with the arrival of the Obama administration is, they didn't really have time to build trust before they had to make big, difficult decisions.

In combat operations in places like Afghanistan, we often confronted the specter of dangerous people with powerful weapons who were a threat to their community and to our soldiers. Our aim was to quickly determine who in that community was a legitimate actor who could be trusted with a firearm and who was not.