COMMANDER'S ADDRESS President Barack Obama thanks U.S. Sen. Dick Lugar of Indiana, center right, and former U.S. Sen. Sam Nunn of Georgia, center, for their work to help denuclearize countries after the fall of the Soviet Union at National Defense University in Washington D.C., Dec. 3, 2012. SHARE: Download: Full Size (0.05 MB) Credit: VIRIN: 337976-T-SXW78-844.jpg Photo Gallery