1555 - Official Acceptance of the Protestant Reformation
The Augsburg Interim that ended the Schmalkaldic War a few years previously did nothing to appease the Protetsants, and in 1552 Protestant German forces in Saxony, supported by the Catholic French King Henry II, rebel against the Catholic Holy Roman Emperor Charles V. A Protestant victory results in the temporary Peace of Passau, granting the Protestants religious freedom until a more permanent treaty is agreed. That treaty comes in 1555 with the Peace of Augsburg, which establishes Protestantism as an official religion alongside Catholicism in the Holy Roman Empire. Imperial princes are henceforth allowed to choose between Protestantism or Catholicism as the official religion for their territories.
In the former Alemannic territories of the Holy Roman Empire Charles II, Margrave of Baden-Durlach, adopts the Protestant Reformation in 1556, supported by Christoph, Duke of Württemberg, who had already converted to Protestantism some 15 years earlier, whilst the Margraviate of Baden-Baden remains Catholic.
Although a significant step forward in soothing religious tensions, the treaty applies only to the Lutheran Protestant tradition, and specifically excludes other Protestant traditions such as the Calvinists and Anabaptists. In 1618 continued tensions between the Catholic Holy Roman Empire and the Protestant Calvinists of Bohemia (modern day Czech Republic) will lead to The Bohemian Revolt, the first act in the devastating Thirty Years' War.