I think the First World War is really the outlier with just how HIGH the casualty numbers were. Soldiers weren’t dying on battlefields in those numbers before, and haven’t really since.
The wall along the front of Père Lachaise cemetery in Paris has the names of all the Parisians who died in the war. Walking along it, it seems to go on forever. It’s very similar to the American Vietnam Memorial in DC. The key difference being that the French one has the names of about 90k people from a single city in France that died in the span of four years, while the American one has about 60k names from the entire USA who died over the course of more than a decade. That’s just a staggering loss of life.