Derek Chollet, former U.S. Assistant Secretary of Defense for International Security Affairs, now counselor and senior advisor for security and defense policy at The German Marshall Fund of the United States, and Jeffrey Rathke, senior fellow and deputy director of the Europe Program at The Center for Strategic and International Studies, preview with host Carol Castiel the upcoming NATO Summit in Warsaw, Poland and examine how Great Britain’s recent vote to leave the European Union might affect the NATO alliance.