Thirteen families are undertaking the painful process of mourning the deaths of young troops killed by a suicide bomber at a Kabul airport gate. President Biden stood at Dover Air Force Base when their flag-draped coffins arrived. Most of the families will say goodbye to their loved ones at national cemeteries across the country and their graves will be marked with a recognizable gravestone that makes clear their service and their sacrifice.

This recognition of fallen soldiers is a product of a memorial tradition that dates back to the Civil War. The unprecedented scale of human carnage in that war fueled a transformation in mourning and memorialization. Virtually each family, North and South, was touched by the war, and most by death, whether by losing direct or extended family members, friends or neighbors. The practices established in that war have served as the foundation for traditions of memorialization for every war since.

The Civil War differed radically from any conflict before. It was the world’s first major industrial war, fought with the materials, production and weapons borne of mechanization and made in factories. This also created new and more efficient ways to kill and maim more people, and to do it faster than before.

A greater number of people served, suffered and died than in the past — and battles created hundreds and thousands of dead in a matter of days or hours. For example, at Gettysburg, three days of fierce fighting in July 1863 left an estimated 7,100 dead, who had to be removed from the summer heat and buried. Men dug trenches for them and tried to keep track of names as best they could.

When President Abraham Lincoln arrived for the dedication of the Gettysburg national cemetery in November, he delivered the first presidential speech at a battlefield burial ground. This act reflected how the federal government had slowly assumed responsibility for creating burial places for the fallen soldiers over the course of the war.

In the fall of 1861, the War Department had instructed commanders to find burial sites and keep records. This task proved difficult. The Army didn’t issue identification, so in anticipation of death, some soldiers resorted to pinning pieces of paper with their names and hometowns to their uniforms — a process finally replaced in 1899 by today’s “dog tags.”

As the scale of battles grew, so too did the death tolls, leading to the need to create larger permanent burial spaces. Local cemeteries couldn’t absorb all the bodies, although some contracted with undertakers to bury those who died near makeshift military hospitals. The great majority ended up in hastily created burial grounds, some shallow and in poor condition by the war’s end.

A survey of battle burial grounds in 1865 revealed that they were already falling into disrepair, with hastily installed wooden headboards rotting and falling. These burial sites reflected the geography of the fighting itself, with large and small graveyards scattered across a landscape where great battles and smaller skirmishes had taken place.

By 1867, a frustrated Quartermaster General’s Office set out to expand the system of national cemeteries by consolidating the burial grounds and formalizing their operation and administration.

Those national cemeteries looked very different than what people anticipated — and it was by design. Much more than mere graveyards, they were beautifully landscaped spaces with winding roads and paths that connected vistas and views, meandering among gravestones and monuments that told the living why those lost should be remembered.

Their appearance came from landscape architect Frederick Law Olmsted (best known for designing New York’s Central Park and a lover of winding paths and pretty vistas), who wanted each to be a “sacred grove.” The purpose of the national burial grounds focused on a heightened sacred function, and Olmsted thought that their physical tranquility would help guide the ways people responded to and interacted with these spaces, unlike those in cities borne of the rural cemetery movement.

When we picture them in our mind’s eye, they’re generally expansive spaces with rows and rows of neatly aligned white slabs, all the same size and height, punctuated only by an occasional monument or tree. These are not spaces people visit to just wander and be with nature, to see trees and flowers, to get away from crowded cities. It is here that we recognize those who, as Lincoln said at Gettysburg, “gave the last full measure of devotion.”

And yet, even marking them was a subject of controversy. Initially, the graves of the first 100,000 or so soldiers relocated into national cemeteries had wooden markers that would need replacement in a few years. A growing public clamor pressured the War Department to permanently commemorate those who had died.

In 1873, the first standardized stone slab marker we recognize today appeared — polished white stone, curved top, name, rank and state etched on the face. The design has changed over time, but the basic form remains.

Thanks to the Civil War, the military extended the honor of such a marker to veterans of past wars as well. And the practice continued as the United States fought subsequent conflicts. Today the white stone markers are taller, wider and thicker to make them more durable. After World War I, the War Department authorized placing a religious symbol on the markers as well.

The U.S. government decided in 1879 that soldiers can be buried anywhere and still have a wartime gravestone. Now when we walk around cemeteries — private and public, large and small, urban, suburban and rural — we can readily recognize those who served in the military. And those 10 men and three women, whose remains arrived at Dover Air Force Base on Aug. 29, can have one too. No matter where they are buried, we’ll be able to recognize their ultimate sacrifice with an immediate glance, even from a distance.