The Polish Jews came under German rule after the Nazi invasion of Poland on September 1, 1939, and during 1940 most of them were being assembled in ghettos. The one in Warsaw was the largest of these and reached almost half a million residents. For the Jews incarcerated in these prisons, the situation in the ghettos was frequently terrible: hunger, disease and forced labour claimed many victims. With the crowded living conditions, starvation diets, and little sanitation, hundreds of thousands of Jews died of disease and hunger.
Added to this, beginning in the summer of 1942, constant deportations to the extermination camps began to empty out the ghettos. There were three types of ghettos created: Open ghettos, Closed or sealed ghettos, and Destruction or extermination ghettos towards the end of the war.Across Europe, the Nazis established over 1,000 ghettos for the segregation and deportation of Jews.