There were camps in every country occupied by the Nazis. The transportation of prisoners was often carried out under horrifying conditions using rail freight cars, in which many died before they reached their destination. Concentration camps also existed in Germany itself, and while not specifically designed for extermination, many concentration camp prisoners died because of harsh conditions or were executed.
After the invasion of Poland, the Nazis created ghettos to which Jews and Gypsies were confined, until they were eventually shipped to death camps and killed. The Warsaw Ghetto was the largest, with 380,000 people and the Łódź Ghetto, the second largest, holding about 160,000, but ghettos were instituted in many cities. On July 19, 1942, Heinrich Himmler ordered the start of the deportations of Jews from the ghettos to the death camps.