Prisoners of War, World War I
These numbers include figures for the fronts in France (west), Italy (south), Balkans and Russia (east), and the numbers are very much in dispute because every country wants to look the best. Some of these POW numbers also include "missing."
Source: Great Britain. War Office. Statistics of the Military Effort of the British Empire during the Great War (London, 1922); Michel Huber. La population de la France pendant la guerre (Paris, 1931); PBS: The Great War