Incoming commander of U.S. Central Command Gen. James N. Mattis, takes the flag signifying the assumption of command from outgoing acting Lt. Gen. John Allen, center, while Defense Secretary Robert M. Gates looks on during an assumption of command ceremony at MacDill Air Force Base, Fla., Aug. 11, 2010. - Incoming commander of U.S. Central Command Gen. James N. Mattis, takes the flag signifying the assumption of command from outgoing acting Lt. Gen. John Allen, center, while Defense Secretary Robert M. Gates looks on during an assumption of command ceremony at MacDill Air Force Base, Fla., Aug. 11, 2010.