About 1.5 million East European Jews-mostly from Poland, the Ukraine, and Russia-survived the Second World War behind the lines in the unoccupied parts of the Soviet Union. Some of these survivors, following the German invasion of the USSR in 1941, were evacuated as part of an organized effort by the Soviet state, while others became refugees who organized their own escape from the Germans, only to be deported to Siberia and other remote regions under Stalin's regime. This complicated history of