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Anniversary Of Sept. 11th Attacks Marked At Pentagon

(L-R) Chairman of the Joint Chiefs of Staff Michael Mullen, Secretary of Defense Leon Panetta, and Vice President Joe Biden observe a moment of silence during the time of impact at a remembrance ceremony at the Pentagon September 11, 2011 in Arlington, Virginia. The United States is commemorating the 10th anniversary of the terrorist attacks of September 11, 2001 which resulted in the deaths of 2,753 people when two hijacked planes crashed into the World Trade Center. Security has been heightened in both New York City and Washington D.C. following a terrorist threat about a car bomb. (Photo by Win McNamee/Getty Images)

9/11 Pentagon ceremony

Remembering the September 11, 2011 attack on the Pentagon.