The Treaty of Westphalia, signed in 1648, signified a pivotal moment in European power dynamics as it ended the Thirty Years' War and established principles of sovereignty and non-interference in domestic affairs. This treaty marked the beginning of the modern state system, recognizing the rights of states to govern themselves without outside interference. It also led to a shift in the balance of power, curtailing the influence of the Catholic Church in political matters and allowing for the emergence of nation-states. The Westphalian model laid the foundation for contemporary international relations and diplomacy.