Few figures from the Middle Ages occupy historians in Germany as much as the Staufer Emperor Frederick I. Barbarossa does to this day. The intensive examination of his imperial politics and the events that took place in the second half of the 12th century concerning the Italian part of the empire form the thematic focus of the following study. The emphasis is on uncovering the backgrounds that led to disputes between the empire and the apostolic see. In this context, the confrontation between the German ruler and the Curia, particularly with Pope Adrian IV, his successor Alexander III, and their closest ally, the Lombard League, will also be scrutinized. Furthermore, the different relationship networks between the involved parties will be illuminated to enhance understanding.