The beginning of the modern state system in Europe after the Peace of Westphalia in 1648 marked a significant shift in international relations. This treaty ended the Thirty Years' War and established the principle of state sovereignty and non-intervention in the internal affairs of states. It recognized the rights of coexisting sovereign states and laid the groundwork for the modern concept of international law. The Peace of Westphalia fundamentally changed the political landscape of Europe, setting the stage for the development of nation-states and the complex system of diplomacy that characterizes global politics today.