With the fall of Poland, thousands of POWs were taken by the German Army, and millions more before the war was over. The question of what to do with those POWs would lead to some of the worst atrocities of the war.
Large numbers of Allied POWs were taken as the Nazis stormed across Europe. Hundreds of thousands of French soldiers were taken to Germany and put into forced labor camps. By 1945 the majority of forced laborers in Germany were French. Two hundred thousand British and Dominion troops were captured in France, Greece, Crete and North Africa. Thousands of Americans were shot down over Germany or taken in combat in Italy. They were all sent to camps in Germany.
When Germany invaded the Soviet Union, the huge encirclements of 1941 swallowed whole Russian army groups. Some five million Soviets went into captivity, including large numbers of Russian women. Only one out five would come home again.
Unlike the indigenous civilian populations that were sent to concentration camps, the POWs were held separately in different camps unless they were found guilty of some war crime and were sent to a death camp. For the Western POWs, that meant they had a better chance at survival then either the concentration camp prisoners or their comrades in Japanese hands. Around 17% of Western Allied soldiers died while in German detention; Allied soldiers in Japanese hands had less than a 50% chance of survival.
Different branches of the German armed forces ran different camps. The RAF and USAAF fliers shot down over Germany were taken to camps run by the Luftwaffe after interrogation. Ground troops were taken to camps run by the Wehrmacht.
As the war progressed against Germany, Hitler issued a series of orders that led to many massacres of western Allied troops. The Commando Order, issued after Dieppe on October 18, 1942, called Commandos “bandits” and that they should be shot on sight. This led to the execution of Americans dropped into Czechoslovakia by parachute, Canadians killed by the 2nd SS Panzer Division in Normandy in June 1944, and Norwegians attempting to land by boat. The total number of Allied soldiers killed by the Germans will never be known.