The Edict of Restitution was proclaimed by Ferdinand II, Holy Roman Emperor in Vienna, on 6 March 1629, eleven years into the Thirty Years' War. Following Catholic military successes, Ferdinand hoped to restore control of land to that specified in the Peace of Augsburg (1555). That treaty's "Ecclesiastical Reservation" had prohibited further secularization of lands held by the Catholic church after 1555, disallowing any transfer of such lands to Protestant control. However, as the Holy Roman Empire descended into the Thirty Years' War, weak emperors had been unable to enforce this provision against Protestant encroachments. Background The Diet of Speyer (1526) introduced the principle of cuius regio, eius religio: in essence, agreeing to disagree within the Holy Roman Empire. With that principle confirmed by the Peace of Augsburg, large-scale violence between Lutherans and Catholics in Germany was temporarily avoided. Some Protestant princes interpreted this principle to mean that the Peace of Augsburg allowed secularization of lands held under Catholic church officials who converted to Protestantism. With the Emperors unable to enforce an interpretation more favorable to them, lands traditionally held by the Catholic church continued to be secularized in this way after the Peace of Augsburg. In Europe at this time, and in particular the German states within the Holy Roman Empire, control over land and its inheritance was frequently contested, as it was the main source of both power and wealth. Noble families sought to control as much land within the extended family as possible, including by appointing younger sons prince-bishops or prince-abbots. This system created strong incentives to convert to Protestantism and secularize land, thereby seizing control of it from the Catholic Church. The Edict The "Edict of Restitution" attempted to retroactively enforce Ferdinand's interpretation of the "Ecclesiastical Reservation" of the Augsburg treaty, effectively undoing changes in control over large areas of land. This had a strong polarizing effect, causing the approximately 1,800 states of the Holy Roman Empire to form disparate, violently opposed blocs. If fully effected, it would have changed the rulers of the already secularized Archbishopric of Bremen and Archbishopric of Magdeburg, 12 bishoprics, and over 100 religious houses throughout the German states. What was implemented resulted in a great transfer of power and property from the Protestants to the Catholics, compounding a divisive religious struggle with conflict for dynastic power among many smaller German princes, who might otherwise have stayed neutral. This dramatic expansion