For most Americans, Memorial Day is a time of celebration and remembrance. It’s a day when we honor the sacrifice of our service members who gave “the last full measure of devotion” for our freedom.

But while most families are attending Memorial Day parades and listening to family members tell stories about their days in the service, others are calling for the destruction of the memorials created to celebrate our military heroes.

Over the past several years, a handful of atheists, humanists, and others have launched an all-out-war on some of our most cherished veterans memorials.  These groups are committed to stripping all religious imagery from public view – including imagery chosen by military families not for religious purposes but merely to honor their dead.

For example, the Mt. Soledad National Veterans Memorial near San Diego, California was erected in 1954 to honor Korean War veterans. Although it has become a beloved feature of the community, the ACLU waged a decades-long battle to force the government to demolish the memorial simply because it features a cross.

Lest anyone think this a West Coast phenomenon, the Bladensburg, Maryland World War I Veterans Memorial—erected almost 100 years ago by the local post of The American Legion and mothers who wished to honor their sons who died during World War I—is now the subject of a similar lawsuit by a humanist group. The group’s sole objection to the monument is this: that mothers chose to remember their sons with a cross-shaped monument.

Even memorials in the heartland are not immune to attack. In March, Americans United threatened a lawsuit against the “Welcome Home, Soldier” Monument in Albia, Iowa because it includes a row of 21 white crosses in the style of military gravestones. The crosses, engraved with the names of veterans, symbolize the 21-gun salute, one of our military’s highest honors.

If these activist groups are successful in their misguided mission to strip the nation of any religious imagery, including those used to honor our fallen service members, the consequences could be staggering.

What will happen to the Tomb of the Unknown Soldier, who is known “but to God?” What will be the fate of the Argonne Cross Memorial, erected in 1923 in honor of Americans who died fighting in France? Will the Canadian Cross of Sacrifice in Arlington National Cemetery—a symbol of Canada’s gratitude to the thousands of American “dough boys” who volunteered for Canada during World War I—still stand? Will the Normandy crosses, erected to honor the heroism of our service members on D-Day, be destroyed?

These memorials—whether in California, Maryland, Iowa, or in hundreds of other locations across the national landscape—remind us that freedom is not a birthright. It was purchased at a terrible price: nothing less than the blood of America’s sons and daughters.

This Memorial Day, as we relax with family and watch parades, let’s remember the price paid by our military service members and their families. And let’s honor them by committing to defend the monuments erected in their memory.

Throughout our nation’s proud history, our veterans have given their lives for us. The least we can do is guard and defend the memorials that honor them.

Mike Berry is a veteran of the United States Marine Corps.