The Chairman of the Joint Chiefs of Staff, Gen. Martin E. Dempsey, sings “White Christmas” with the military service members stationed at Bagram Air Field, Afghanistan, Dec. 9. 2014. Dempsey was joined on his USO Holiday Troop Tour, by Country music artist Kellie Pickler, retired Chicago Bears middle linebacker Brian Urlacher, actress Dianna Agron, comedian Rob Riggle, actress Meghan Markle, Washington Nationals pitcher Doug Fister and USO President Dr. J.D. Crouch II. (U.S. Army Photo by Sgt. Adam Erlewein, 4RSSB Public Affairs.)(Released)