Military captivity was one of the most pervasive experiences in both world wars. In World War I an estimated 8 million soldiers became prisoners of war (POWs), while in World War II the number was perhaps as high as 35 million. If one adds the number of soldiers captured in the multitude of wars that occurred between the signing of the Hague Convention of 1899 (the first major international treaty relating to the treatment of POWs) and the signing of the Geneva Convention in 1949, the number of captured soldiers approximated 50 million.

The difficulty of assessing the number of POWs during this period stems not only from the general unreliability of wartime statistics during the first half of the twentieth century, but also from the deliberate obfuscation by some armies of their casualty figures. Moreover, because the designation “prisoner of war” came to be applied only to interstate warfare (rather than intrastate or non-state warfare), many de facto combatants did not acquire this legal designation at all (or lost it for various reasons). In other words, the evolving legal codification of POW treatment in the period 1899–1949 affected not only the treatment of military captives, but also the framing of captivity itself.