PAYING TRIBUTE The 36th Chief of Staff of the Army Gen. George W. Casey, Jr. salutes the headstone of the Army's 15th Chief of Staff Gen. George C. Marshall at Arlington National Cemetery, Va., on the U.S. Army's 234th birthday, June 14, 2009. Casey and Sgt. Maj. of the Army Kenneth O. Preston visited the gravesites of previous Army chiefs of staff and sergeants major of the Army. SHARE: Download: Full Size (0.07 MB) Credit: VIRIN: 274335-X-EMR70-684.jpg Photo Gallery