GUEST SPEAKER Defense Secretary Robert M. Gates addresses the audience during the U.S. Army Chief of Staff change of responsibility ceremony at Fort Myer, Va., April 10, 2007. Gen. George W. Casey took over as chief of staff from Gen. Peter J. Schoomaker. SHARE: Download: Full Size (0.02 MB) Credit: VIRIN: 156893-M-AWT25-268.jpg Photo Gallery