Sixty-seven years ago tomorrow, Allied troops looked off the back of landing craft floating off the beach at Normandy into what seemed the mouth of hell itself. It was 6:30 a.m., and Operation Overlord, which was intended to open a second Allied front against the Nazis in occupied France, had begun. The enemy was ensuring that the Allies would pay for every inch of beach they gained.

It must have looked like a suicide mission to many of the young men who threw themselves into the water and made their way to the beach, hauling 80 to 100 pounds of equipment with them. And in fact, for thousands of them, the assault would be their death. But Allied generals considered a beachhead in France to be the crucial foundation of their plan to take back Europe from Hitler’s army. And five beaches along the coast of Normandy were chosen as the sites where the Allies would press their attack.

The day would become known as D-Day, and it is still remembered solemnly in America, Britain and France.

More than 5,000 ships and 4,000 ship-to-shore transports were used in the attack, supported by 13,000 aircraft. But it was the men, more than 150,000 of them and most from the U.S. — men who put themselves in harm’s way despite what appeared to be insurmountable odds against them — that the annual commemoration of the invasion honors.

On the first day of the operation alone, Allied troops suffered more than 10,000 casualties, including 4,000 deaths. Most of those casualties were at heavily defended Omaha Beach, located at the center of the movement against German forces. And most of the dead and wounded Allies were Americans.

But Gen. Dwight D. Eisenhower had called the operation a crusade in which “we will accept nothing less than full victory,” and the Americans were eager to defeat the fascist threat to the world that Hitler represented. Back at home, families were making sacrifices so that the nation’s resources could be put toward the war effort, and across the Atlantic, their sons, husbands and fathers were preparing to lay down their lives in the same effort.

There’s a reason these people are often referred to as the “Greatest Generation.” They saw the great challenge before them and marched ahead, resolute in their determination to overcome. The Allies’ D-Day invasion of Normandy was only one example of that determination in action, but it still stands as evidence of the power of American sacrifice.

Each year that passes, fewer and fewer of the brave men who stormed the beaches amid a hail of opposing gunfire and artillery remain with us to tell about their experience. If you meet one today, take a moment to ask him to share his story, and then shake his hand and thank him for being made of the stuff that made America great.