European wars of religion of the German states and, to a lesser extent, the Low Countries and Italy, while bankrupting many of the powers involved. The war ended with the Treaty of Münster, a part of the wider Peace of Westphalia. During the war, Germany's population was reduced by 30% on average. In the territory of Brandenburg, the losses had amounted to half, while in some areas an estimated two thirds of the population died. The population of the Czech lands declined by a third. The Swedish army alone, which was no greater a ravager than the other armies of the Thirty Years' War,
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