The significance of the Peace of Westphalia lies in its role in establishing the modern state system in international relations. Signed in 1648, this treaty ended the Thirty Years' War in Europe and recognized the principle of sovereignty for states. It marked a shift away from religious conflicts to a focus on territorial integrity and political authority. The Westphalian model laid the groundwork for contemporary diplomacy, establishing norms that govern the interactions between states, such as respect for national borders and non-interference in domestic affairs—key tenets of international law.