Update at 10:40 a.m. ET

On the 13th anniversary of the Sept. 11 attacks, President Obama, first lady Michelle Obama and Vice President Joe Biden gathered on the White House lawn to observe a moment of silence.

The solemn commemoration of the attacks that killed some 3,000 people came just hours after the president addressed the nation on a strategy to "degrade and destroy" Islamic State militants in Iraq — a stark reminder that the so-called "war on terror" appears to be far from over.

At a ceremony at the Pentagon, the president said "we carry on, because as Americans, we do not give in to fear. Ever."

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