Nazi eugenics
In his Second Book, which was never published during the Nazi era, Hitler praised the ancient Greek city of Sparta. In Sparta, all newborn infants were examined carefully.  Any infant that seemed weak, sick, or had any kind of disability was killed.  Only the healthy, strong children were allowed to live.  This meant that they were the only people alive to have children and continue the Spartan race.  Hitler praised this early model of eugenics: