President Barack Obama participates in the Armed Forces farewell tribute to Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, right, at Joint Base Myer-Henderson Hall, in Arlington, Va., Sept. 30, 2011.

President Barack Obama participates in the Armed Forces farewell tribute to Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, right, at Joint Base Myer-Henderson Hall, in Arlington, Va., Sept. 30, 2011.