As we gather with family and fire up the grill this weekend, let’s pause to remember the true meaning of Memorial Day. Far more than just the unofficial start of summer, today is a solemn day of remembrance dedicated to the brave men and women who made the ultimate sacrifice while serving in the U.S. military.

Originally known as Decoration Day, the tradition began in the wake of the Civil War. In 1868, General John A. Logan declared a nationwide day of remembrance to decorate the graves of fallen soldiers with flowers. Over time, the holiday evolved to honor American service members lost in all conflicts. In 1971, Congress declared Memorial Day a federal holiday, placing it on the last Monday of May to ensure a unified national day of reflection.

“Our flag does not fly because the wind moves it. It flies with the last breath of each soldier who died protecting it.” — Unknown

Today, we honor that profound legacy. Let’s hold their bravery in our hearts and express our deepest gratitude for the freedoms we enjoy every day.

Have a safe and meaningful Memorial Day.

Twenty-one steps south. Face east 21 seconds. Face north 21 seconds. Twenty-one steps north. Face east 21 seconds. Face south 21 seconds. Repeat until relieved.

Thus is the meticulous routine performed by the select few chosen for the honor of guarding the Tomb of the Unknown Soldier, located in Arlington National Cemetery, just outside of Washington, D.C. These Tomb Guard Sentinels, elite volunteer members of the U.S. Army’s 3rd U.S. Infantry Regiment, watch the Tomb 24 hours a day, 365 days a year, rain or shine — and have done so for almost 80 years.

The Tomb of the Unknown Soldier was constructed in 1921, after Congress approved the burial of an unidentified U.S. soldier from World War I, with other Unknowns interred since. The Tomb has been guarded year-round continuously since 1937, when the first 24-hour guards were posted. Since April 1948, sentinels from the 3rd U.S. Infantry Regiment, also known as the “Old Guard,” have been watching over the hallowed memorial.

The above video shows a complete changing of the guard ceremony edited together from three different ceremonies all recorded on May 20, 2015. To watch the video at full resolution, be sure to choose the 4K option in the YouTube player.

The video was shot and produced by Justin Scuiletti. Special thanks to Arlington National Cemetery and Sgt. 1st Class Nicolas Morales for helping in the production of this video.