The U.S. has reached a sad milestone in the 11-year war in Afghanistan. As of last week, 2,000 American troops have lost their lives in the war. These are tough times for the U.S. and NATO campaign in Afghanistan. So called "insider killings," in which U.S. and NATO troops and trainers are attacked by the Afghans working with them are on the rise. In just the past two weeks, nine Americans have been killed in insider attacks. Dr. Andrew Exum is a senior fellow at the Center for a New American Security, who served two tours in Afghanistan.