The peace treaty that ended the Thirty Years' War in 1648 is known as the Peace of Westphalia. This series of treaties, held in Münster and Osnabrück, concluded a devastating conflict that ravaged much of Europe, particularly the Holy Roman Empire. The Westphalian treaties are significant for establishing principles of national sovereignty and religious tolerance, leading to the recognition of state boundaries and independence. They also marked the decline of Spanish hegemony and the emergence of France and Sweden as major powers. The Peace of Westphalia is often cited as a foundational moment in the development of the modern international system.