Holger Richter has systematically examined the operational psychology of the Ministry for State Security of the GDR (MfS) and the scientific results of the Chair of Operational Psychology. The book provides a brief overview of the history, the key figures involved, and a content analysis of the most important documents of operational psychology. It addresses the question of the extent to which operational psychology was indeed a "scientific" psychology. Operational psychology is compared with the official GDR psychology of the time. A chapter on the language of the Stasi aims to highlight its particular psychological function and contribute to the understanding of the discussed texts. Nearly 40,000 pages of Stasi files and originals from the legal college of the MfS in Potsdam-Eiche were included in this work.