Jewish by birth, Bettelheim grew up in a secular family. After the Anschluss (political annexation) of Austria on March 13, 1938, the National Socialist (Nazi) authorities sent Austrian Jews and political opponents to the Dachau and Buchenwald concentration camps where many were brutally treated, and tortured or killed. Bettelheim was arrested some two months later on May 28, 1938, and was imprisoned in both these camps for a combined total of ten and a half months before being released on April 14, 1939.[9][10] While at the Buchenwald camp, he met and befriended the social psychologist Ernst Federn. As a result of an amnesty declared for Adolf Hitler's birthday (which occurred slightly later on April 20, 1939), Bettelheim and hundreds of other prisoners were released.[citation needed] Bettelheim drew on the experience of the concentration camps for some of his later work.