During World War II, Nazi Germany engaged in deliberate extermination policies towards Soviet Union prisoners of war (POWs). This resulted in some 3.3 to 3.5 million deaths, about 60% of all Soviet POWs. During Operation Barbarossa, the Axis invasion of the Soviet Union, and the subsequent German–Soviet War, millions of Red Army prisoners of war were taken. Some of them were arbitrarily executed in the field by the German forces, died under inhumane conditions in German prisoner-of-war camps and during ruthless death marches from the front lines, or were shipped to Nazi concentration camps for extermination.