Auschwitz--the largest and most notorious of Hitler's concentration camps--was founded in 1940, but the Nazis had been detaining Jews in camps ever since they came to power in 1933. Before Auschwitz unearths the little-known origins of the concentration camp system in the years before World War II and reveals the instrumental role of these extralegal detention sites in the development of Nazi policies toward Jews and in plans to create a racially pure Third Reich.

Investigating more than a dozen camps, from the infamous Dachau, Buchenwald, and Sachsenhausen to less familiar...