James Mattis is a retired four-star Marine Corps general and former defense secretary. This op-ed is adapted from remarks prepared for a Memorial Day address in his hometown, Richland, Wash.

On Memorial Day this year, we may be keeping social distance from one another, but that cannot detract from the sense of closeness, the sense of community and the sense of shared sacrifice that we feel for one another on a day when we come face-to-face with the human cost of freedom.

What do we owe our fallen and their families on this day? Remembrance, for sure, yet we also owe a keen awareness of what they fought to defend: this great big experiment we call America.

The Founders — most of whom were military veterans — knew that the nation they were forming was an experiment, a test of the idea that people could live together and rule themselves, guided by the spirit of cooperation. The Constitution they devised was itself hammered out among those willing to compromise, giving birth to this experiment.

Upon being elected the first U.S. president, Gen. George Washington at his inauguration said, “the preservation of the sacred fire of liberty, and the destiny of the republican model of government, are justly considered as deeply, perhaps as finally staked, on the experiment entrusted to the hands of the American people.”

In his wisdom and humility, Washington saw the daunting challenge of keeping our experiment alive, and the role of American citizens in proving to the world that people didn’t need a king or a tyrant: We, the people, could rule ourselves.

Following the nation’s rugged birth, this radical idea has periodically needed defending by patriots, many of whom have given their lives and whom we honor on this day.

Those include the Union soldiers who gave their last full measure to hold the nation together and cast out the heinous practice of slavery, imported from the Old World, that had been a defect since America’s birth.

In President Abraham Lincoln’s short address dedicating a military cemetery at Gettysburg in 1863, he exhorted his listeners to resolve “that these dead shall not have died in vain — that this nation, under God, shall have a new birth of freedom — and that the government of the people, by the people, for the people, shall not perish from the earth.”

Lincoln knew he had to say it out loud: This republican form of government could, in fact, perish — unless we fought for it, unless we dedicated our lives to living up to its ideals, unless we were willing to compromise with one another, while working always to improve the fairness of life for every American.

Nearly a century later, President John F. Kennedy — a World War II veteran — echoed that message in his 1961 inaugural address when he said we must be ready to “pay any price, bear any burden, meet any hardship . . . to assure the survival and success of liberty.”

Generation after generation of patriots have given their all to keep this precious legacy alive. That is why we gather every year to pay our respects to those who went down swinging to protect and defend our Constitution and our way of life.

Soldiers, sailors, airmen, Coast Guardsmen and Marines serve a country that, even in its most raucous times, is worth defending. They swear to do so at their personal peril, signing a blank check to all the American people, payable with their lives.

Our veterans have learned the hard way, having lost buddies in battle, that this nation has no ordained right to exist. America’s freedoms do not stand unassailed. Dictators and authoritarians look with fear on our freedom, our experiment, our republican model — a model that has long served as an inspiration to oppressed peoples everywhere.

We are most indebted to our veterans who fell, and their families, for the survival of this experiment. They can never be fully repaid, but we begin to do so by respecting one another in this land of boundless possibilities, because those who faced down danger and paid the price on our behalf deserve no less.

Many of us enjoy America’s freedom by an accident of birth, yet we all live free in this land by our own choice. It is our responsibility to show respect and genuine friendship to each other as fellow citizens — including those with whom we sometimes disagree — by unifying around our radical idea. That is how we can meet our ultimate responsibility: to turn over to the next generation a republic in better shape than we received it.

Those who fell while wearing our nation’s cloth in defense of freedom, and the Gold Star families of their survivors, paid an everlasting price. Every American owes them a commitment to keeping vibrant the experiment for which they died.

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