German prisoners in an unidentified French prison camp. A prisoner of war is a person, whether combatant or non-combatant, who is held in custody by an enemy power during or immediately after an armed conflict. During WWI, about 8 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. The German Empire held 2.5 million prisoners; Russia held 2.9 million, and Britain and France held about 720,000, mostly gained in the period just before the Armistice in 1918. Photo taken by French Pictorial Service, 1917-18.