As the war in Ukraine demonstrates, accurate numbers of those killed or injured in combat are hard to come by. This column describes the ‘Morts pour la France’ database, which contains individual-level data on the 1.3 million French fatalities during WWI. The database improves our grasp of geography (rural, poorer, less industrialized areas were harder hit), of battle-specific violence (the deadliest day in French history took place during the Second Battle of Champagne), and of conflict technology (the share of infantry decreased over time while the share of artillery increased).