Modern European state systems refer to the political organization of European nations that emerged from the Peace of Westphalia in 1648, characterized by sovereign states with defined territorial boundaries and centralized authority. This system marked a shift from feudal allegiances to national identities, laying the groundwork for modern diplomacy, international law, and nation-states. The evolution of these systems was significantly influenced by various social, religious, and political upheavals, particularly during the Reformation and Catholic Reformation periods.