The Thirty Years' War in Europe was concluded by the Peace of Westphalia in 1648. This treaty is significant for its role in ending the war, which had devastated much of Europe and involved numerous nations. The Peace of Westphalia established a new political order based on the principle of state sovereignty, acknowledging the independence of various territories and granting them control over their internal affairs. Additionally, it marked the decline of Catholic dominance in Europe, fostering greater religious tolerance. The treaty's principles laid the groundwork for modern international relations and diplomacy, shaping the future geopolitical landscape of Europe.