Why Russia Is Rebuilding Its Nuclear Arsenal

On Friday evening, at the end of the final nuclear security summit of his tenure, President Barack Obama took a swipe at his Russian counterpart, Vladimir Putin, for standing in the way of nuclear disarmament. Obama's remark was pointed, calling out Putin by name, and it cast a rare bit of light on the personal clash between the two presidents on an issue that both of them see as central to their legacies.