The Thirty Years' War is the worst European war of the period between the Hundred Years' War and the First World War. Its principal area of operation — the empire — lost approximately a third of its population to the combined effects of military action, displacement, famine and disease between 1618 and 1648, with substantial regional variation: parts of central and northern Germany, particularly the swathes repeatedly crossed by armies (the Palatinate, Saxony, Thuringia, Brandenburg, Mecklenburg, Pomerania), lost more than half their inhabitants; the Bohemian-Moravian plateau and the Wends along the Baltic coast were similarly devastated; only the geographic margins (the Habsburg hereditary lands, Bavaria, the southern Catholic territories on the Danube, and the western Rhineland) emerged with merely catastrophic rather than apocalyptic losses. The war was the constitutional crisis of the post-1555 settlement; its peace settlement of 1648 was the empire's final constitutional consolidation; and the central European population would not recover its 1618 levels until well into the eighteenth century.
The Defenestration of Prague
The war began as a Bohemian constitutional revolt. The Bohemian Estates, predominantly Protestant (Lutheran, Calvinist, and Utraquist) but constitutionally subject to a Habsburg king under the elective Bohemian crown, had received in 1609 a Letter of Majesty from the Habsburg emperor Rudolf II guaranteeing extensive religious liberties. Rudolf's successors — Matthias and then the Styrian Habsburg Ferdinand II, elected King of Bohemia in 1617 — were less inclined to honour the guarantees, and Ferdinand in particular was a pupil of the Counter-Reformation Jesuits with a programmatic commitment to reCatholicising the Bohemian crown. On the 23rd of May 1618, three royal officials at Prague Castle were thrown out of a third-floor window by an aggrieved delegation of Protestant nobles. They survived the fall — landing in a manure heap in the moat — but the Defenestration of Prague was the trigger of the war.
The Bohemian Estates deposed Ferdinand as king of Bohemia in 1619 and elected the Calvinist Frederick V of the Palatinate in his place. Frederick — also the son-in-law of James I of England, and through his electoral position a prince-elector of the empire — accepted the Bohemian crown over the public advice of the more cautious Protestant German princes. The Habsburg counterstroke came at the Battle of White Mountain near Prague on the 8th of November 1620, in which a Catholic League army under Maximilian I of Bavaria and the imperial general Tilly destroyed the Bohemian-Palatine force in two hours. Frederick fled (acquiring the historical nickname "the Winter King", for his one-winter reign), Bohemia was reconquered for the Habsburgs, the Bohemian Protestant nobility was executed, exiled or dispossessed (the great Bohemian intellectual emigration of the 1620s carried Comenius, Skopius and others into central European exile), and the Bohemian crown lands were systematically reCatholicised. The Palatinate, Frederick's electoral territory, was occupied by Spanish and Bavarian troops; the electoral dignity was transferred from the Palatine Wittelsbachs to the Bavarian Wittelsbachs in 1623.
The Danish phase
The war's second phase opened with Danish intervention. The Lutheran king Christian IV of Denmark — also duke of Holstein and therefore an imperial prince — feared the consolidation of Habsburg-Catholic power along the Baltic and entered the war in 1625 with substantial English, Dutch and French subsidies. The Habsburg-Catholic forces, by now under Albrecht von Wallenstein (the Bohemian-Protestant turned Catholic mercenary commander, raised by Ferdinand II as Duke of Friedland) as well as Tilly's Catholic League army, defeated Christian's forces at Lutter in 1626 and Wolgast in 1628. Christian sued for peace at Lübeck in 1629, recovering his Danish-Holstein dukedom but abandoning his imperial-prince allies.
The same year, 1629, the Edict of Restitution proclaimed by Ferdinand II ordered the return to Catholic control of all church property secularised by Protestant princes since the cut-off date of 1552. The Edict was a substantial overreach: it threatened to dispossess Lutheran princes who had quietly converted ecclesiastical territory across three generations, including the substantial Brandenburg-Pomeranian and Mecklenburg gains. The Catholic League — particularly Maximilian of Bavaria — was alarmed at the implication that the empire was becoming a Habsburg absolutist project rather than a balanced Catholic federation, and pressed Ferdinand to dismiss Wallenstein, which he did at the Diet of Regensburg in 1630. The dismissal was costly: with Wallenstein gone and the Edict actively alienating Protestant moderates, the empire was unprepared for the next external intervention.
The Swedish intervention
Gustavus Adolphus of Sweden — the Lion of the North, the most innovative military commander of the seventeenth century, the developer of the combined-arms tactical doctrine that would dominate European warfare for the next 150 years — landed in Pomerania in July 1630 with 13,000 Swedish-Finnish troops. The Swedish intervention was principally motivated by the Baltic-strategic interest in preventing Habsburg consolidation along the Pomeranian and Mecklenburg coasts, but it was funded substantially by Cardinal Richelieu's France — the most consequential Catholic-Protestant alignment of the war, demonstrating that the religious frame was now subordinate to dynastic-political calculation. The Swedish army defeated Tilly at Breitenfeld outside Leipzig in September 1631 (the largest Swedish victory of the war, and the first major Catholic defeat), occupied much of central and southern Germany during 1632, and reached Munich. At the Battle of Lützen on the 16th of November 1632 the Swedes won tactically but Gustavus Adolphus was killed.
The Swedish phase continued under his chancellor Axel Oxenstierna and the Heilbronn League of Protestant German princes. Wallenstein, recalled by the desperate Habsburgs in 1632, conducted ambiguous negotiations with the Swedes and Saxons in 1633–34 and was murdered by his own officers at Cheb in February 1634 on Ferdinand's orders. The Battle of Nördlingen of September 1634 was the major Spanish-Imperial victory of the period, broke the Swedish position in southern Germany, and produced the Peace of Prague of 1635 — a partial settlement that suspended the Edict of Restitution and reconciled Saxony and Brandenburg with the emperor.
The French phase
The Peace of Prague might have ended the war if France had not entered it openly. Richelieu declared war on Spain in May 1635 and on the emperor in 1636. The final twelve years of the war (1636–1648) were the French phase: Franco-Swedish-Dutch armies operating in concentric campaigns against the Spanish-Habsburg forces, with intermittent peace negotiations beginning in 1641 and the substantive peace negotiations opening at Münster and Osnabrück in 1644. The war ran on at a substantially lower intensity than the 1620s-30s, but the central German countryside continued to be devastated; the major French victory at Rocroi in 1643 (under the future Great Condé, then twenty-two years old) effectively ended the Spanish military reputation as the dominant force in European warfare.
The Peace of Westphalia
The Peace of Westphalia — actually two parallel treaties, the Treaty of Münster (between the empire and France-Spain-Dutch) and the Treaty of Osnabrück (between the empire and Sweden), signed on the 24th of October 1648 — was the largest and most consequential European peace settlement of the early modern period. Its substantive provisions: Calvinism was added to the religious peace alongside Lutheranism and Catholicism; the territorial cuius regio principle was retained but with substantial revisions; the Edict of Restitution was definitively rescinded; the imperial estates received Landeshoheit — full territorial sovereignty, including the right to conclude treaties with foreign powers — subject only to the explicit reservation that such treaties not be directed against the emperor or the empire; Switzerland and the Dutch Republic were recognised as independent of imperial sovereignty; substantial territorial cessions were made to France (the Alsatian Landgraviate, Metz, Toul, Verdun) and Sweden (Western Pomerania, Bremen-Verden, Wismar); and Brandenburg was substantially compensated with eastern Pomerania and the Magdeburg-Halberstadt secularised bishoprics, the foundation of the later Brandenburg-Prussian rise.
The empire that emerged from Westphalia in 1648 was a federation of approximately 1,800 effectively sovereign territorial units under a Habsburg emperor whose authority was now substantively limited by the imperial constitution. The institutional structure that the next century-and-a-half would inhabit — the perpetual diet at Regensburg, the imperial courts at Wetzlar, the religious-confessional balance, the slow rise of Prussia and the structural decline of imperial authority outside the Habsburg hereditary lands — is the subject of the next two chapters.
End of Chapter V