Gisevius was born in Arnsberg in the Prussian Province of Westphalia. After law school, he joined the Prussian Interior Ministry in 1933 and was assigned to the newly-formed Geheime Staatspolizei, or Gestapo. After joining the Gestapo, he immediately had disagreements with his senior, Rudolf Diels, and was discharged. He continued with police work in the Interior Ministry. When Himmler took over Police functions in 1936 in the German Reich, he removed Gisevius from office. Gisevius later transferred to the Reich Ministry of the Interior. Although he had no position of power, he maintained connections, notably to Arthur Nebe, that kept him informed of the political background. Gisevius joined the secret opposition to Hitler, began gathering evidence of Nazi crimes (for use in a later prosec