World War I casualties
The total number of military and civilian casualties in World War I were about 40 million: estimates range from 15 to 19 million deaths and about 23 million wounded military personnel, ranking it among the deadliest conflicts in human history.
Chemical weapons in World War I
Phosgene was never as notorious in public consciousness as mustard gas, but it killed far more people, about 85% of the 90,000 deaths caused by chemical weapons during World War I.