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WASHINGTON DC - SEPTEMBER 11: United States President Barack Obama, left, with US Secretary of Defense Ash Carter, center, and US Marine Corps General Joseph F. Dunford Jr., Chairman of the Joint Chiefs of Staff, right, at the Pentagon Memorial in Washington, DC during an observance ceremony to commemorate the 15th anniversary of the 9/11 terrorist attacks, Sunday, September 11, 2016.<br />
Credit: Dennis Brack / Pool via CNP/MediaPunch