European wars of religion new political order that is now known as Westphalian sovereignty. The conflicts began with the Knights' Revolt (1522), a minor war in the Holy Roman Empire. Warfare intensified after the Catholic Church began the Counter-Reformation in 1545 against the growth of Protestantism. The conflicts culminated in the Thirty Years' War (1618–1648), which devastated Germany and killed one-third of its population. The Peace of Westphalia (1648) put an end to the war by recognising three separate Christian traditions in the Holy Roman Empire: Roman Catholicism, Lutheranism, and Calvinism. Although many European leaders were 'sickened' by the religious bloodshed by 1648, religious
Hessian War Peace Congress mediated by Duke Ernest of Saxe-Gotha and which resulted in a unification and peace treaty that was sealed in April 1648, ahead of the Treaty of Westphalia itself. Before the Westphalian Peace Treaty, Cassel fought one last time against the imperial side, winning the Battle of Wevelinghoven in the Rhineland, together with other Protestant troops. Darmstadt, however, was not involved in this battle. Under the Unification Treaty between Cassel and Darmstadt, Upper Hesse was permanently divided. Darmstadt had to give up a significant part of Upper Hesse to Cassel, not least Marburg and other occupied territories, including the