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Anniversary of Sept. 11th Attacks Marked At Pentagon

Members of the Secret Service counter sniper team and other security take positions on the roof before a memorial service at the Pentagon September 11, 2011 in Arlington, Virginia. Vice President Joseph R. Biden, Secretary of Defense Leon E. Panetta, Chairman of the Joint Chief of Staff Navy Admiral Mike Mullen and others will attend a memorial service at the Pentagon Memorial to commemorate the 10th anniversary the September 11, 2001 terrorist attacks on the United States. (Photo by Brendan Smialowski/Getty Images)

9/11 Pentagon ceremony

Remembering the September 11, 2011 attack on the Pentagon.