U.S. Army Staff Sgt. Derrik Browne and Sgt. Jason Andrade provide security during a visit by Army officials to Bala Hesar in Gardez, Afghanistan, June 27, 2011. Bala Hesar is a fortress in Gardez that is home to a new Afghan quick reaction force. Browne and Andrade are assigned to the 1st Cavalry Division's Operations Company, Headquarters Battalion. U.S. Army photo by Spc. Adam L. Mathis

Defense Secretary Robert M. Gates shakes hands with President Barack Obama while Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, applauds during the Armed Forces Farewell Tribute to honor the retiring secretary at the Pentagon, June 30, 2011. DOD photo by Cherie Cullen

Defense Secretary Robert M. Gates and Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, left, greet Vice President Joe Biden upon his arrival at the Pentagaon before the Armed Forces Farewell Tribute to honor the retiring secretary, June 30, 2011. DOD photo by Cherie Cullen

Defense Secretary Robert M. Gates shakes hands with Defense Department employees as he departs the Pentagon for a final time as secretary, June 30, 2011. DOD photo by Cherie Cullen

Defense Secretary Robert M. Gates addresses the audience while President Barack Obama and Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, look on, during the Armed Forces Farewell Tribute to honor Gates at the Pentagon, June 30, 2011. DOD photo by Cherie Cullen

The U.S. Army Old Guard Fife and Drum Corps marches on the parade field during the Armed Forces Farewell Tribute to honor Defense Secretary Robert M. Gates at the Pentagon, June 30, 2011. DOD photo by U.S. Air Force Tech. Sgt. Jacob N. Bailey

Defense Secretary Robert M. Gates renders a salute during a pass and review at the Armed Forces Farewell Tribute in his honor at the Pentagon, June 30, 2011. DOD photo by U.S. Air Force Tech. Sgt. Jacob N. Bailey

The 3rd U.S. Infantry Salute Guns Platoon renders honors at the Armed Forces Farewell Tribute to honor Defense Secretary Robert M. Gates at the Pentagon, June 30, 2011. DOD photo by U.S. Air Force Tech. Sgt. Jacob N. Bailey