The moment
On 25 September 1555 the Imperial Diet at Augsburg agreed that each prince and free city of the Empire could choose either Catholicism or the Lutheran Augsburg Confession for its territory, a rule that jurists later summed up as cuius regio, eius religio. Calvinists, Anabaptists and others were excluded, and the settlement held until the Thirty Years' War began in 1618.
People: Charles V, Ferdinand I