Selecting remains for the Tomb of the Unknown Soldier was always going to be difficult. There was the emotional toll of the process, but there were also thorny practicalities that had to be addressed even in the midst of the remembrance. First, organizers had to be fairly certain that the remains in question would never be identified.

Officers have generally been given the task of randomly selecting one individual for interment in the tomb. But that doesn’t exactly happen on the battlefield or in a foreign country. According to PBS, the first individual buried in the tomb was selected from four soldiers. In Chalons-sur-Marne, France, the caskets were rearranged to conceal their original burial spots and Sgt. Edward F. Younger was tasked with selecting the American honoree. He indicated his random choice by placing roses on the casket lid. The three remaining caskets were transported for burial in a Paris cemetery. The selected individual was placed in a more decorated casket and prepared for transport across the Atlantic Ocean to Arlington National Cemetery.

Arlington National Cemetery reports that a similar process was used for the selection of the World War II and Korean War unknowns, which all took place in 1958. For World War II, one individual each was picked to represent both the European/North African and Pacific Theaters of the war. Major General Edward J. O’Neill indicated his choice for the first region by placing a wreath on one of 13 caskets.

As you may well have guessed, the position of tomb guard isn’t one that’s open to just anyone. According to Reuters, becoming a sentinel at the Tomb of the Unknown Soldier requires an intensive selection, training, and inspection process. Before someone can even begin to contemplate guarding the tomb, they must undergo a series of tests to ensure that they understand the history of the monument and how to present themselves. Any sloppiness in their quarters or uniform is not to be tolerated. And, yes, tomb guards really do have to wear wet gloves. It reportedly improves their grip on the rifle that’s part of their kit, and certainly no one wants to fumble their firearm in a solemn changing of the guard ceremony in front of a crowd.

That said, there are some misconceptions about what it means to be a tomb guard. Some sources will plainly state that guards, even when off duty, aren’t allowed to curse or drink alcohol. Setting aside just how the military would enforce such rules — would an officer be following them around at all times to make sure they don’t even have a beer? — that’s simply not true. Yet, it’s clear that the volunteers who pass muster and become guards for the tomb take it very seriously.

If you carefully observe the changing of the guard ceremony at the Tomb of the Unknown Soldier (and also really enjoy precisely counting things), then you’ll learn that the number of steps and seconds facing the tomb at certain points in the process are all very, very specific. According to Reuters, those moves are nearly all based on the number 21, in reference to the 21-gun salute that is a pretty serious ceremonial honor in the military.

Per the U.S. Army Center of Military History, the salute has its roots in a number of similar honors throughout history, including 21-gun salutes practised earlier in other nations. That exact number of weapons firing also changed over the years; for instance, 1810 saw only 17 guns in the honor, referencing the number of states in the Union at the time. Even today, the number of guns in a salute reflects a person’s rank or occasion’s seriousness, with 21 being the maximum.

While the Tomb of the Unknown Soldier certainly does not celebrate the fact of its existence, it’s still there to memorialize the immense sacrifice not just of a single person, but their family and community. Yet, when it comes to the unknown soldier selected to represent those killed in the Vietnam War, things became complicated. That’s because he wasn’t really unknown at all.

According to the Washington Post, one of the motivations behind selecting a service member for the tomb was to help ease the considerable tensions that had built up during the Vietnam War. The hope was that political divisions could be at least somewhat smoothed over by the honor accorded to the individual buried there. And, for a while, military officials thought they had selected a good candidate: a pilot whose remains were recovered from his crashed aircraft in the jungle and returned to the U.S. Army in 1972.

As a 1998 DNA test would prove, those remains belonged to Air Force 1st Lt. Michael Joseph Blassie (pictured). And the South Vietnamese Army patrol that came across the wreck found his remains in association with Blassie’s identification. Yet, some allege that the Army intentionally dragged its feet and refused to officially identify Blassie, though members of his family long suspected the move and lobbied for the test. When the truth came out, the Blassie family had Michael reinterred in St. Louis. Now, the Vietnam crypt of the Tomb of the Unknown Soldier remains empty.

Currently, there are no remains interred in the Tomb of the Unknown Soldier that date from after the end of the Korean War. As Lieutenant Blassie’s story demonstrated, the advance of identification methods like DNA analysis have made it increasingly difficult for a soldier’s remains to become truly unknown.

Even soldiers who died in wars many decades ago now stand a chance of finally being identified and their remains returned to living family members. The New York Times reports that, in 2018, 55 individual sets of remains were returned to the U.S. from North Korea. The service members in question had died in North Korea during the Korean War, from 1950 to 1953.

A Department of Defense group known as the Defense P.O.W./M.I.A. Accounting Agency (D.P.A.A.) was tasked with securing those identities and helping to connect them with families. Forensic anthropologists and other researchers conduct analysis of skeletal remains, take samples for DNA testing, and compare with preexisting medical records to make those identifications. While putting a face and name to a set of remains isn’t always easy or straightforward, the ability to do so means that it’s nearly impossible to deem an individual unknown anymore. In all likelihood, there will be no new interments in the Tomb of the Unknown Soldier in the future.