In the 16th century the factors of confessional propaganda and “public opinion” become very important for public power. Each princedom, defining the principles of imperial and "foreign" policy, was guided by the confessional motivation of the prince and all structures of territorial power (courts institutions, Landtags, city councils), as well as that part of society that had a consolidated opinion in religious affairs (universities, Landeskirchen). Johann Casimir (1543—1592), the son of the Elector Palatinate Friedrich III and regent for his nephew Friedrich IV, began to form the pro-calvinist confessional-political course of the Palatinate. He organized and led the several expeditions to help the French and Dutch Calvinists. The accession to the throne of the Lutheran Ludwig VI made it impossible for Johann Casimir to use the resources of the Palatinate. However, he organized informational support for his actions in defense of Protestantism. Johann Casimir prepared for publication “Confessio Fidei” of Friedrich III (1577, in German, Latin and French), and three “open letters”: about the military actions of Protestants in France (1576, in German and French), about the reasons for the military expedition to the Netherlands (1578, in German, Latin and Dutch), about the reasons for the military expedition in support of the Elector of Cologne (1583—1584, in German and French). Was only religious propaganda the aim of the prince? Or was Johann Casimir guided not the least by political motives and ambitions? Historiography focused on attempts of the Palatinate electors to unite German Protestants at the turn of the 16th — 17th centuries (Friedrich IV and Friedrich V), however, we can assume that the “plan of action” appeared already in Johann Casimir. His interventions were not successful, but allowed the Palatinate to claim leadership among the German Protestants.