As the families of those killed on Sept. 11 gathered Wednesday morning in New York, Pennsylvania and Virginia to mark the anniversary of the attacks, the costs of what happened 12 years ago are still being borne across the globe.
With the nation once again in the midst of a debate about America's role in the world and the wisdom of launching military strikes, the memorial ceremonies offered not just an occasion to pay tribute, but a moment to take stock.
At the Pentagon, where 184 people were killed, President Barack Obama noted the continuing threat.
"Let us have the strength to face the threats that endure, different though they may be from 12 years ago, so that as long as there are those who would strike our citizens, we will stand vigilant and defend our nation," he said.
The president paid tribute to the four Americans, including Ambassador J. Christopher Stevens, who died one year ago in an attack at the U.S. Consulate in Benghazi, Libya.
In New York, the anniversary ceremony has taken on the familiarity of ritual.
Bruni Sandoval has come each year to remember her friend, Nereida De Jesus. "It helps a little," she said.
The ceremony at ground zero began with bagpipers and drummers; the Brooklyn Youth Chorus performed the national anthem.
At 8:46 a.m., when the first plane struck the north tower, there was a moment of silence. In Washington, Obama and Vice President Joe Biden, their wives by their sides, stood on the White House lawn, heads bowed.
At 9:03, a second moment of silence marked the moment a second plane hit the south tower. There would be four more moments of silence interrupting the reading of the names — twice to mark the time when each tower fell and to mark the moments of the attacks on the Pentagon and on Flight 93, which crashed into a field in Pennsylvania.