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.
Prisoner of war
During World War I, about eight million men surrendered and were held in POW camps until the war ended. All nations pledged to follow the Hague rules on fair treatment of prisoners of war, and in general the POWs had a much higher survival rate than their peers who were not captured. Individual surrenders were uncommon; usually a large unit surrendered all its men. At Tannenberg 92,000 Russians surrendered during the battle. When the besieged garrison of Kaunas surrendered in 1915, 20,000 Russians became prisoners. Over half the Russian losses were prisoners as a proportion of those captured, wounded or killed. About 3.3 million men became prisoners.