Def. Sec. Gates retires at Pentagon in Virginia

U.S. President Barack Obama shakes hands with Secretary of Defense Robert Gates as Chairman of the Joint Chiefs of Staff Adm. Michael Mullen looks on during Gates' Armed Forces Farewell Ceremony on the Pentagon River Parade Field in Arlington, Virginia, on June 30, 2011. Former CIA Director Leon E. Panetta will become the 23rd Secretary of Defense, replacing Gates on July 1. UPI/Roger L. Wollenberg