

The Holocaust in Nazi-occupied Poland took the lives of three million Polish Jews, destroying an entire civilization. Poles represented the largest number of people who rescued Jews during the Holocaust. To date, 6,863 Poles have been awarded the title of Righteous Among the Nations by the State of Israel, over 700 of which received their awards posthumously.
Between October 1939 and July 1942 a system of ghettos was imposed for the confinement of Jews. The Warsaw Ghetto was the largest in World War 11, with 380,000 people crammed into an area of 1.3 square miles. The Łódź Ghetto held about 160,000. Other Polish cities with large Jewish ghettos included :
Ghettos were also established in hundreds of smaller settlements. Living conditions were terrible with overcrowding, dirt, lice, lethal epidemics such as typhoid and hunger resulted in countless deaths. The ghettos were connected with the formation of highly secretive killing centers built at about the same time and designed exclusively for the rapid elimination of Polish Jews in ghettos.
Six extermination camps were established throughout Poland by 1942.
Sources:
MUSEUM of the HISTORY of POLISH JEWS