How did these books become part of the libraries' collections?
During the Nazi dictatorship from 1933 to 1945, libraries profited in various ways from raids carried out by the Nazi regime. They were beneficiaries of large stocks of illegally confiscated and looted books taken from persons and institutions persecuted for racial and political reasons. They received books and entire libraries that were brought to Germany as booty from the conquered countries of Central, Western, Eastern and Southeastern Europe during the war.
Numerous Nazi organisations were involved in the raids, such as Einsatzstab Reichsleiter Alfred Rosenberg (ERR), Sonderkommando Eberhard von Künsberg at the Foreign Office under Foreign Minister Joachim von Ribbentrop, and the Sicherheitsdienst (SD) led by Reinhard Heydrich. However, distribution to the libraries was mainly organized by an organization called "Reichstauschstelle" (Reich exchange agency), which controlled the academic library system in the Nazi state. By the end of the war, that agency had hoarded over a million volumes in numerous centers throughout Germany.
After WW2, Nazi-looted assets also found their way into libraries through purchases from antiquarians and through donations. Therefore, Nazi-looted assets and booty can also be found in libraries that were founded only after 1945. In many cases, there is no documentation about the acquisition of those books by the libraries.