As your family sits down to enjoy a meal together this Christmas, spare a thought or prayer for families who have an empty seat at their table where a brave son, daughter, husband, or wife would sit if they were not serving overseas in the military.

Because America enjoys relative peace this Christmas, it’s easy to forget that we are still a country at war. Our troops abroad and their families at home don’t have the same sense of calm that Bethlehem had on a starry night two millennia ago.

More than 215,000 American military personnel are stationed overseas. About 22,000 are in danger in Afghanistan, Iraq, and Syria, working to eradicate terrorism, the Taliban, and the Islamic State. Another 68,000 are in Japan or South Korea, within easy striking distance of North Korea's armaments should the tyrant, Kim Jong Un, have a temper tantrum.

Hundreds of thousands of others are stationed inside the U.S., and many can’t make it home for Christmas, while others could be called away at a moment’s notice. Even U.S. Cyber Command staff will work on Christmas to make sure your new electronic gadgets are protected from digital threats.

While we sit by the fire and open presents with our families, Christmas is just another day on duty for many soldiers, sailors, marines, and airmen. As one Pentagon official wrote, using the Navy as an example: “Sailors are performing missions that cannot stop for the holidays. Christmas is just another day for sailors manning their posts aboard submarines with nuclear weapons. Sailors launching aircraft from the USS Theodore Roosevelt in the Persian Gulf may have time for Christmas services.” (Not that this means our military doesn’t have any Christmas fun — For more than 60 years, NORAD has had the important task of tracking Santa.)

American servicemen and women choose to serve, and they don’t ask for special thanks or privileges in return. In “The Soldier's Night Before Christmas,” a soldier abroad and alone tells a tearful Santa Claus:

Don’t cry, this life is my choice;
I fight for freedom, I don’t ask for more,
my life is my God, my country, my Corps.

That only makes them all the more worthy of our gratitude.

We should give a special thanks to those who give up a normal Christmas to defend our nation and our First Amendment right to celebrate Christmas and every other religious holiday. We can make sure troops have the equipment and support they need to defend themselves and us, and to stay out of harm’s way, and ensure that when troops come home they have high-quality healthcare and job prospects or an education waiting for them.

It's pleasant to wish that American troops could be whisked home every Christmas for 48 hours, but military service during the holidays has been a tradition since the dawn of America as an independent nation. The precedent, like so many other good ones, was set by Gen. George Washington, who crossed the Delaware River with his troops on Christmas night 1776, en route to a crucial surprise attack in the Revolutionary War.

As Thomas Paine wrote two days before that, on Dec. 23, 1776, “These are the times that try men's souls. The summer soldier and the sunshine patriot will, in this crisis, shrink from the service of their country; but he that stands by it now, deserves the love and thanks of man and woman.”