Christophe Receveur, of France, unfurls an American flag he bought six months ago in Gettysburg, Pa., to mark D-Day on Thursday on Utah Beach, Normandy.

Christophe Receveur, of France, unfurls an American flag he bought six months ago in Gettysburg, Pa., to mark D-Day on Thursday on Utah Beach, Normandy. / AP

President Biden marked the 80th anniversary of the D-Day invasion that helped liberate Europe from Nazi Germany on Thursday, attending a ceremony at Normandy American Cemetery alongside French President Emmanuel Macron.

Veterans are awarded a high honor

World War II veterans — dozens of whom were welcomed as returning heroes when they arrived in France this week — were also at the event, a mix of celebrating freedom, remembering the terrible sacrifices it requires, and honoring veterans who put their lives on the line.

"On behalf of the American people and as commander in chief, it's the highest honor to be able to salute you here in Normandy," Biden told the veterans.

"Here you came, to join our efforts with your own soldiers, and to make France a free nation," Macron told the former service members. "And you are back here today — at home, if I may say."

Under clear and sunny skies, Macron presented a group of veterans with the Legion of Honor, France's highest decoration, pinning medals to their jackets as the crowd applauded. The cemetery and its memorial sits just inland from the famed Omaha Beach, on the shore where more than 150,000 U.S. and Allied troops streamed ashore in a massive amphibious assault.

Event nods to Ukraine's war against Russia

As it evoked that historic and bloody day, the event also took note of a current conflict: Europe is once again a place of war, as Russia seeks to pummel neighboring Ukraine into submission.

"Ukraine has been invaded by a tyrant bent on domination," Biden said, referring to Russian President Vladimir Putin.

The U.S., NATO and its allies stand with Ukraine and won't "walk away," Biden said. He warned of a ripple effect of violence and aggression, should Russian succeed in subjugating Ukraine.

"The autocrats of the world are watching closely to see what happens in Ukraine, to see if we let this illegal aggression go unchecked. We cannot let that happen."

Worldwide, he added, democracy is more at risk now than it has been at any other time since World War II ended.

Both Biden and U.S. Defense Secretary Lloyd Austin called on the U.S. and its allies to uphold the spirit of D-Day.

"We still seek a world where aggression is a sin and where human rights are sacred and where all people can live in freedom," Austin said. "At this time in history, we must again stand firm against aggression and tyranny."

Austin also had a message to the veterans who sat nearby: "You saved the world. Gentlemen, we salute you."

Biden touts engagement over isolation

"What the allies did together 80 years ago far surpassed anything we could have done on our own," Biden said, urging Americans not to forget that lesson.

"Together we won the war," he said. "We rebuilt Europe, including our former enemies. It was an investment in what became [a] shared and a prosperous future."

Investing in NATO and other alliances is in the self-interest of the U.S., the president added.

"Isolationism was not the answer 80 years ago and is not the answer today," Biden said. "We know the dark forces that these heroes fought against 80 years ago. They never fade, aggression and greed, the desire to dominate and control to change borders by force. These are perennial."

Military cemeteries like the one at Normandy show the cost of freedom, Biden said.

"Remember, the price of unchecked tyranny is the blood of the young and the brave," Biden said. "In their generation, in their hour of trial, the Allied forces of D-Day did their duty. Now the question for us is, in our hour of trial, will we do ours?"