Fifty years ago last month, American troops were authorized to begin aiding the cause of the South Vietnamese against the communist north. It may be hard for people of a certain age to believe so many years have passed, or that those young soldiers who eventually returned to a troubled and divided nation now are graying veterans.

Yet in ceremonies around the country today, their deeds will be honored in ways many of them might not have imagined possible once that war became unpopular. Those commemorations began on Memorial Day. They need to continue, in some form or another, for as long as the nation survives.

It has been said that the United States is more of an idea than a traditional nation. Almost from its beginning, people have migrated here from all over the world because of that idea. They have come because of what it could mean for them, their children and an endless line of future generations.

But the idea has a price, and it seems no generation can pay it fully. Each has an installment come due.

Today's price is being paid on battlefields in Afghanistan, at embassies and consulates worldwide where attacks and other dangers are a constant concern, and at surveillance posts where intelligence officers try to stay a step ahead of enemies who would launch attacks similar to those of 9/11. But it also is being paid in homes and schools where children are taught lessons about freedom, brave Founding Fathers who pledged their lives and sacred honor to the liberty of future generations, and of brave men and women who gave "the last full measure," as Abraham Lincoln called it, so that today's Americans could live in peace and prosperity.

More than that, however, it is being paid in voting booths, as millions of Americans peacefully exercise their right to choose leaders, as demonstrated last Tuesday. And it is exemplified in the way losing candidates, even for the most powerful office in the land, by tradition will call and congratulate the winner and peacefully relinquish all claims to the office.

A half-century ago the awful sacrifices paid in Vietnam did not always get the respect they deserved. Too many people had trouble separating the political decisions of war from the willing sacrifices of those non-political souls who waged it.

The experiences of Thomas Collins III, now a retired Air Force lieutenant colonel, as featured recently in USA Today, were sadly not a-typical. Shot down and severely injured, he was beaten and tortured. Bound in ropes, he suffered from infections and was barely fed. When he refused to answer questions during interrogations, he was placed before a firing squad that shot bullets over his head. For seven long years and four months he had no contact from home, stuck in a prisoner of war camp soldiers derisively called the Hanoi Hilton. Yet today he has neither regrets nor bitterness. His efforts, he said, were not wasted.

Veterans Day traces its roots to the 11th hour of the 11th day of the 11th month of 1918, a day of unparalleled optimism and idealism. World War I was over, and it was widely thought to be the war to end all wars.

People of that day couldn't see Germany's humiliation giving rise to Hitler, or the many perceived injustices and opportunities for gain that would spawn despots and violence in a seemingly endless string in years to come.

Those events have placed the American idea in even sharper relief.

What is the best way to honor people like Thomas Collins III for their heroic deeds? Perhaps it is to imagine a world in which they, and the American idea, do not exist, and then dedicate ourselves to making sure such a place never comes about.