America's symbol of military might became a place of mourning Thursday as thousands gathered outside the Pentagon to honor the 184 lives lost there during the 9/11 attacks.

President Bush, speaking at newly unveiled Pentagon memorial, told the audience of victims' loved ones and military personnel that future generations will hail America's response to the terror attacks that shook this nation.

"The day will come when most Americans have no living memory of the events of Sept. 11," Bush said. "When they visit this memorial, they will learn that the 21st century began with a great struggle between the forces of freedom and the forces of terror."

Bush added: "They will learn that this generation of Americans met its duty: We did not tire, we did not falter, and we did not fail."

On Sept. 11, 2001, shortly after the World Trade Center was attacked, terrorists crashed a hijacked airliner into the Pentagon, damaging the west side of the massive building and setting off fires that took hours to contain.

The signature feature of the Pentagon Memorial are its rows of arcing, stainless steel benches, each one representing a person who died in the attacks.

Known as "light benches," each 14-foot long sculpture was built over a basin of trickling water that contains underwater lights to shine on the steel underside at night.

The 184 benches, all of which bear a victim's name, were constructed to match American Airlines Flight 77's path just before it crashed. They were arranged by the victims' ages, so visitors will first see a bench dedicated to Dana Falkenberg, a 3-year-old passenger.

The last bench was dedicated to retired Navy Capt. John Yaminicky Sr., another passenger who was 71.

The memorial was designed by a pair of New York City arhitects and built at a cost of $22 million, without the controversy that has affected New York's still-unfinished memorial.