Treaty of Westphalia

The Treaty of Westphalia (more accurately, the Peace of Westphalia) refers to two related treaties signed in 1648 in the Westphalian towns of Münster and Osnabrück: the Treaty of Münster (between the Holy Roman Emperor and France, and separately between Spain and the Dutch Republic) and the Treaty of Osnabrück (between the Emperor and Sweden, with their respective allies). Together they ended the Thirty Years' War, one of the deadliest conflicts in European history, and recognized the independence of the Dutch Republic and the Swiss Confederation from imperial authority.

Key provisions included territorial adjustments favoring France and Sweden, the reaffirmation and extension of the 1555 Peace of Augsburg principle of cuius regio, eius religio (the ruler determines the religion of the territory), and the addition of Calvinism alongside Lutheranism and Catholicism as tolerated confessions within the Empire. The settlement also confirmed the near-sovereign status of the roughly 300 imperial estates, allowing them to conduct their own foreign policy so long as it was not directed against the Emperor.

In international relations theory, Westphalia is conventionally cited as the symbolic origin of the modern sovereign state system—the so-called "Westphalian sovereignty" model based on territorial integrity, legal equality of states, and non-intervention in domestic affairs. Scholars such as Stephen Krasner (Sovereignty: Organized Hypocrisy, 1999) and Andreas Osiander have challenged this narrative as a 19th- and 20th-century reading projected backward, noting that the treaties themselves do not articulate sovereignty in modern terms. Nonetheless, the Westphalian frame remains foundational vocabulary in IR scholarship, diplomacy, and Model UN debate, particularly when discussing humanitarian intervention, Responsibility to Protect (R2P), and challenges to state sovereignty.