US Secretary of Defense Chuck Hagel (C) and Chairman of the Joint Chiefs of Staff Martin E. Dempsey (R) clap after US President Barack Obama spoke during a memorial service at the National 9/11 Pentagon Memorial September 11, 2013 in Washington, DC. Obama, Hagel and others attended the event to mark the 12th anniversary of terries attacks on the Pentagon and the World Trade Center. AFP PHOTO/Brendan SMIALOWSKI (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)