9 / 21

Mike Mullen, Leon Panetta, Joe Biden

Vice President Joe Biden, from right, Defense Secretary Leon Panetta, and Chairman of the Joint Chiefs of Staff Adm. Mike Mullen participate in commemorative ceremony to honor vicitms of the Sept. 11 attacks during the 10th anniversary at the Pentagon in Washington, Sunday, Sept. 11, 2011. (AP Photo/Charles Dharapak)

9/11 Pentagon ceremony

Remembering the September 11, 2011 attack on the Pentagon.