The Peace of Augsburg established the principle of cuius regio, eius religio—whose realm, his religion—letting each prince determine whether his territory would be Catholic or Lutheran, a landmark in the fracturing of Christian unity in Europe. It brought a fragile peace after years of religious war within the Empire, though it excluded Calvinists and other reformers, planting seeds for future conflict, including the devastating Thirty Years' War.
Charles V, exhausted by decades of struggling to hold his sprawling, religiously fractured empire together, effectively delegated the settlement to his brother Ferdinand, signaling his own resignation from the impossible task of enforcing Catholic unity by force. The agreement did not create religious tolerance in any modern sense; individuals had no personal right to choose their faith, only rulers did, and dissenters were expected to convert or emigrate.
The peace held for over sixty years, an achievement given the era's sectarian violence, but its exclusions proved fatal in the long run. Calvinism spread rapidly through the Palatinate and elsewhere without any legal standing, and the unresolved status of these communities, combined with disputes over confiscated church lands, helped ignite the Thirty Years' War in 1618—a conflict that would kill perhaps a third of the population in some German territories before a new peace was struck at Westphalia.
Key people: Charles V, Ferdinand I