The significance of the Peace of Westphalia, which concluded the Thirty Years' War in 1648, lay in its establishment of a new diplomatic order in Europe. This treaty recognized the principles of state sovereignty and non-interference in the internal affairs of states, marking a shift from religious to secular governance in international relations. It laid the foundation for the modern nation-state system by recognizing the rights of states to self-determine their own religious affiliations. The Peace of Westphalia also brought an end to widespread conflict in Europe and set a precedent for future negotiations and treaties to resolve disputes peacefully.