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.