(CNN) President Joe Biden commemorated those who died serving in the military in Memorial Day remarks at Arlington National Cemetery and urged Americans to honor the fallen by strengthening and protecting the nation's democracy.
"Democracy itself is in peril, here at home and around the world. What we do now -- what we do now, how we honor the memory of the fallen will determine whether or not democracy will long endure," Biden said.
The President said: "We owe the honored dead a debt we can never fully repay. We owe them our whole souls. We owe them our full best efforts to perfect the union for which they died."
Biden said the nation must honor the sacrifices of generations of service members "by sustaining the best of America while honestly confronting all that we must do to make our nation fuller, freer and more just."
"Empathy is the fuel of democracy," the President said. "Our willingness to see each other not as enemies, neighbors, even when we disagree, to understand what the other is going through."
He spoke of the rising wave of autocratic rule across the world and argued, as he often does, that "liberation, opportunity, justice are far more likely to come to pass in an democracy than an autocracy."
"This nation was built on an idea, the only nation in the world built on an idea. Every other nation is built on ethnicity, geography, religion, etcetera. We were built on an idea, the idea of liberty, an opportunity for all," Biden said.
He continued: "We've never fully realized that aspiration of our founding, but every generation has opened the door a little wider and every generation has opened it wider and wider to be more inclusive."
Biden said the diversity of the nation and its armed forces has been "an incredible strength," and noted Americans of all backgrounds, races, identities and sexual orientations have sacrificed their lives to defend the nation's democracy.
"Remember their sacrifice, their valor and their grace," Biden said. "Remember their smiles, their loves, their laughter, their essential vibrant and transcendent humanity."
The President spoke about the death of his own son, Beau Biden, who was an Iraq War veteran. Sunday marked the sixth anniversary of Beau Biden's death.
"To those who mourn a loved one today, Jill and I have some idea how you're feeling. Our losses are not the same, but that black hole you feel in your chest, as if it's going to suck you into it, we get," Biden said.
He said the anniversary of his son's death is a difficult time of year for him and his family and that he always feels close to his son on Memorial Day.
"It can hurt to remember, but the hurt is how we feel and how we heal," Biden said.
Beau Biden was the attorney general of Delaware and a member of the Delaware National Guard, and died in 2015 at the age of 46 from brain cancer.
Earlier on Monday, Biden, first lady Jill Biden, Vice President Kamala Harris, second gentleman Doug Emhoff, Defense Secretary Lloyd Austin and Chairman of the Joint Chiefs of Staff Gen. Mark Milley participated in a wreath-laying ceremony at the Tomb of the Unknown Soldier at Arlington National Cemetery.
Last month, Biden visited the graves of US troops killed in Afghanistan and Iraq at the cemetery after announcing he was withdrawing all US troops from Afghanistan. The President said he would withdraw US troops from the country before September 11, which is the 20th anniversary of the 9/11 terror attacks.
This story has been updated with additional information.