Peace of Westphalia

The Peace of Westphalia refers to a pair of treaties concluded in 1648 that brought an end to the Thirty Years’ War in the Holy Roman Empire and the concurrent Eighty Years’ War between Spain and the Dutch Republic. The settlement involved a complex array of European powers, including the Habsburg rulers of Austria and Spain and their Catholic allies, pitted against Protestant states such as Sweden and various German principalities, as well as Catholic France, which aligned itself with the anti-Habsburg coalition. Although later scholarship in international relations has often portrayed the Peace of Westphalia as the foundation of modern concepts of state sovereignty, some historians argue that such interpretations are largely retrospective developments of the nineteenth and twentieth centuries, shaped by contemporary debates about sovereignty rather than seventeenth-century realities.
The treaties reshaped political and religious structures within the Holy Roman Empire, redefined territorial relations across Europe, and introduced settlements intended to prevent a recurrence of prolonged religious conflict.

Background to the Negotiations

By the mid-seventeenth century, Europe had been devastated by nearly continuous conflict. The Thirty Years’ War, beginning in 1618, became the deadliest of the continent’s religious wars, evolving from a confessional struggle within the Holy Roman Empire into a wider geopolitical confrontation. Simultaneously, the Eighty Years’ War, initiated around 1568, was fought for Dutch independence from Habsburg Spain, supported by Protestant England.
The Thirty Years’ War underwent several phases, involving numerous domestic and foreign actors aligned either with the Catholic League or the Protestant Union (later the Heilbronn League). The Peace of Prague (1635) resolved many of the specifically religious elements of the conflict, but the rivalry between France and the Habsburgs then took precedence. With estimates suggesting that between 4.5 and 8 million people perished in the conflict, the impetus for a comprehensive peace grew pressing.

Negotiation Sites and Preparations

Initial peace discussions began in Cologne in 1636 between France and the Holy Roman Emperor, though these were hindered by French demands for the inclusion of all their allies, including states within the Empire. A preliminary agreement among Sweden, France, and the Empire was reached in Hamburg in 1641, setting the stage for a broader peace congress.
The main negotiations were held in Westphalia, in the cities of Münster and Osnabrück, chosen for their religious and political balance. Münster, re-Catholicised in 1535, was exclusively Catholic, while Osnabrück was a mixed Lutheran–Catholic city under alternating confessional administration. Sweden preferred Osnabrück, which had been under Protestant control since 1633, whereas France negotiated primarily in Münster.
The congress was unprecedented in its scale. Although no plenary session ever took place, 109 delegations representing 16 European states, 66 Imperial Estates (speaking for 140 Imperial States), and 27 special interest groups arrived between 1643 and 1646, with departures continuing until 1649. The peak period of diplomatic activity occurred between January 1646 and July 1647.

Principal Delegations and Participants

The French delegation was led by Henri II d’Orléans, Duke of Longueville, supported by Claude d’Avaux and Abel Servien. Sweden’s representatives included Johan Oxenstierna and Johan Adler Salvius. The Imperial delegation, representing Emperor Ferdinand III, was headed by Count Maximilian von Trautmansdorff, assisted by Johann Ludwig von Nassau-Hadamar and Isaak Volmar in Münster, and Johann Maximilian von Lamberg and Johann Krane in Osnabrück.
Spain’s delegation, headed by Gaspar de Bracamonte y Guzmán, included notable diplomats and writers such as Diego de Saavedra Fajardo and Bernardino de Rebolledo. Other participants represented the Franche-Comté, the Spanish Netherlands, and various Imperial Estates. The papal nuncio Fabio Chigi (later Pope Alexander VII) and the Venetian envoy Alvise Contarini acted as mediators. The Dutch Republic also sent a significant delegation, although two provinces did not participate. The Old Swiss Confederacy was represented by Johann Rudolf Wettstein.

Treaty Structure

The Peace of Westphalia comprised two principal treaties:

• The Treaty of Münster (Instrumentum Pacis Monasteriensis, IPM), signed between the Holy Roman Emperor and France with their respective allies.
• The Treaty of Osnabrück (Instrumentum Pacis Osnabrugensis, IPO), concluded between the Holy Roman Emperor and Sweden with their respective allies.

On 30 January 1648, parallel to the wider proceedings but separate from the Westphalian settlement, the Dutch Republic and Spain concluded the Peace of Münster, bringing the Eighty Years’ War to an end.

Territorial and Political Outcomes

A substantial portion of the settlement dealt with reorganising authority within the Holy Roman Empire, which had served as the primary theatre of war. Traditional accounts often assert that Emperor Ferdinand III experienced a dramatic loss of authority, with power shifting to the territorial princes. However, recent scholarship challenges this interpretation, suggesting that the reduction of imperial power has been overstated. The Emperor retained meaningful influence in the Imperial Diet and continued to exercise central authority through institutions such as the Aulic Council.
The treaties also confirmed or redefined territorial adjustments. France gained rights over Alsace, while Sweden secured territories in northern Germany, enhancing its influence in the Baltic region. Several Imperial Estates saw their autonomy strengthened, particularly concerning foreign alliances and internal governance.

Religious Settlements

One of the most significant features of the Peace of Westphalia was its religious settlement. The treaties affirmed the right to practise recognised confessions—Catholicism, Lutheranism, and Calvinism—with Calvinism gaining legal recognition for the first time within the Empire. The settlement built on, but did not simply reaffirm, the terms of the Peace of Augsburg (1555).
Contrary to the widespread assumption that the famous principle cuius regio, eius religio (“whose realm, his religion”) was reconfirmed, the settlement introduced a reinterpretation. It held that:

• Certain disputed elements of the Treaty of Augsburg were permanently clarified.
• These interpretations were binding in courts and all Imperial institutions.
• Objections based on prior interpretations were void.
• Crucially, territorial rulers could no longer dictate the private religious practices of their subjects.

Thus, while rulers retained political sovereignty, the private exercise of religious belief was formally removed from princely control. This represented a significant evolution in the governance of religion within the Empire.

Broader Significance

Although the Peace of Westphalia has been widely cited in international relations theory as the foundation of modern state sovereignty—sometimes referred to as Westphalian sovereignty—this interpretation remains debated. Some historians argue that the treaties did not articulate a modern doctrine of territorial sovereignty but instead responded to specific seventeenth-century circumstances of confessional conflict. The attribution of modern sovereign principles to Westphalia, they contend, arose later, during periods when sovereignty was a central political concern.
Nevertheless, the Peace of Westphalia marked a turning point in European diplomacy. It introduced multilateral negotiation practices, acknowledged a broader set of actors within the imperial political order, and ended one of the continent’s most destructive periods of warfare. Its religious provisions contributed to stabilising relations within the Empire, and its territorial adjustments reshaped the political landscape of Europe.