At that time, the Nazis had begun forcing the Jewish residents of occupied cities into closed-off sections known as ghettos. Once there, they were kept as prisoners, often barred from leaving on pain of death. Throughout the course of the war, moreover, more than a thousand such areas were set up in eastern and central Europe.
The Warsaw Ghetto was the largest of those created by the Nazis during World War II. At just 1.3 square miles, it was home to some 400,000 Jews. And for its inhabitants, life was grim, as they were forced to survive on little food and were crammed several people to a room.