the late 1930's the Nazis killed thousands of handicapped Germans by
lethal injection and poisonous gas. After the German invasion of the
Soviet Union in June 1941, mobile killing units following in the wake of
the German Army began shooting massive numbers of Jews and Gypsies in
open fields and ravines on the outskirts of conquered cities and towns.
Eventually the Nazis created a more secluded and organized method of
killing. Six extermination centers were established in occupied Poland
where large-scale murder by gas and body disposal through cremation were
conducted systematically. Victims were deported to these centers from
Western Europe and from the ghettos in Eastern Europe which the Nazis
had established. In addition, millions died in the ghettos and
concentration camps as a result of forced labor, starvation, exposure,
brutality, disease, and execution.