Nazi Germany began building concentration camps (Konzentrationslager) on German soil in 1933, a full six years before the outbreak of World War II. At first, the camps housed political prisoners (mostly communists), but the camps soon began to hold other groups of people deemed socially undesirable: Jews in large numbers, but also Jehovah’s Witnesses, Romani, homosexuals, and the mentally ill. Of the 1.65 million people who were registered prisoners at these camps, roughly one million did not survive. Most camps consisted of a main site and anywhere from three to more than 100 satellite camps. Dachau was a concentration camp. Other notable concentration camps included Bergen-Belsen (where Anne Frank died) and Buchenwald. These camps were distinct from the six extermination camps (Vernichtungslager) where people were sent in even larger numbers for the express purpose of being killed immediately, without being registered as inmates. The extermination camps, which included Auschwitz, Sobibor, and Treblinka, were established in Poland, which had been overrun by the German Army at the start of the war. More than 2.7 million people were murdered at the extermination camps. Of these, at least one million died at Auschwitz. In all, nearly four million people died at the Nazi camps, either by execution or from starvation and disease.

In addition, an estimated two million civilians, mostly Jews, died in mass shootings that did not involve the camps.

The Auschwitz camp system included both concentration and extermination facilities. There is some controversy about the timeline of Frankl’s stays at various camps. He does not mention his family’s two years in Theresienstadt, instead skipping ahead to Auschwitz and leaving the reader with the impression that he spent considerable time there. It has been alleged that Frankl in fact spent only a very short time at Auschwitz, perhaps as little as a few days, before being relocated back to the Dachau system. A mention of “mass transports” to Dachau in the final weeks of the war would be referring to transports from Dachau’s satellite camps to the main camp. It is generally accepted, in any case, that Frankl spent the better part of three years in concentration camps of one form or another.