World War II was - and remains - one of the bloodiest wars in history. Not only did millions of soldiers die in combat but thousands of civilians lost their lives - some for no greater crime than their religious heritage or their nationality. The Soviets, at first allied with the Germans, incarcerated thousands of Polish military officers and reservists in the pre-established Soviet camps of Ostashkov, Starobelsk and Kozelsk. On March 5, 1940, Joseph Stalin and his lieutenants signed an execution order for 25,700 Polish prisoners of war. After months of hardship and interrogation, 14,700 prisoners from these camps were taken to remote areas, murdered with a shot to the back of the head and buried in mass graves. Later, when Germany turned its sights on the Soviet Union, the USSR allied itself with the West.