Three presidents stood somberly side by side on Saturday at the National September 11 Memorial, sharing a moment of silence to mark the anniversary of the nation's worst terror attack with a display of unity.
Presidents Joe Biden, Barack Obama and Bill Clinton all gathered at the site where the World Trade Center towers fell two decades ago -- but Donald Trump was noticeable by his absence.
They each wore blue ribbons and held their hands over their hearts as a procession marched a flag through the memorial, watched by hundreds of Americans gathered for the remembrance, some carrying photos of loved ones lost in the attacks.
Biden is the fourth president to console the nation on the anniversary of that dark day, one that has shaped many of the most consequential domestic and foreign policy decisions made by the chief executives over the past two decades.
The White House released a taped address late on Friday in which Biden also spoke of the "true sense of national unity'' that emerged after the attacks, seen in "heroism everywhere - in places expected and unexpected.''
"To me that's the central lesson of September 11,'' he said. "Unity is our greatest strength.''
Biden arrived in New York on Friday night as the skyline was illuminated by the "Tribute in Light,'' hauntingly marking where the towers once stood.
Following the morning ceremony in New York City, Biden will visit the field near Shanksville where the plane fell from the sky and then will head to the Pentagon, where the world's mightiest military suffered an unthinkable blow to its very home.
Meanwhile, Vice President Kamala Harris spoke at the Flight 93 National Memorial in Shanksville, Pennsylvania, commemorating the heroes who brought down a hijacked plane that was headed for the US. Capitol. Harris praised their courage and the resilience of the American people, and spoke about the unity that Americans experienced in the days following the attacks,
Biden's task, like that of his predecessors before him, was to mark the moment with a mix of grief and resolve. A man who has suffered an immense personal tragedy, Biden speaks of loss with power.
He gave voice to the pain that comes with memories of 9/11 in his video message, saying, "No matter how much time has passed, these commemorations bring everything painfully back as if you just got the news a few seconds ago.''
Robert Gibbs, who served as Obama's press secretary, said for Biden, "It's a moment for people to see him not as Democratic president, but as president of the United States of America.''
"The American people are somewhat conflicted about what they have seen out of Afghanistan the last couple of weeks,'' Gibbs said. "For Biden, it's a moment to try to reset some of that. Remind people of what it is to be commander in chief and what it means to be the leader of the country at a moment of such significance.''
On the 20th anniversary of the attacks, Biden now shoulders the responsibility borne by his predecessors to prevent future tragedy and must do so against fresh fears of a rise in terror after the United States' hasty exit from Afghanistan, the country from which the September 11 attacks were plotted.
It was a war in which 47,000 Afghan civilians lost their lives and who were also, indirectly at least, victims of 9/11.