Nazi eugenics
Because they did not want these "inferior" people in German society, the Nazis decided to get rid of them, using many different strategies.  They began with people with disabilities.  The Nazis forced more than 400,000 people with disabilities to be sterilized (to have surgery that would make it impossible for them to have children).  They also killed over 300,000 people with disabilities in a program called Action T4.  In this program, the Nazis sent people with disabilities to places like Hadamar  and Hartheim Euthanasia Centres to be killed.  These people were killed with lethal injections and poison gas, in vans and gas chambers at the Euthanasia Centres.