CHAIRMAN'S SHAKE U.S. Army Gen. Martin E. Dempsey, chairman of the Joint Chiefs of Staff, gives a challenge coin to U.S. Air Force Tech. Sgt. Scott Douglass during a USO holiday troop visit on Royal Air Force Mildenhall, England, Dec. 10, 2014. Dempsey visited the air base with the USO show troupe, which includes athletes, singers and actors. SHARE: Download: Full Size (0.06 MB) Credit: VIRIN: 214580-E-VSH35-886.jpg Photo Gallery