The Bohemian problem was resolved swiftly. Two Roman Catholic armies, the emperor’s and the League’s, converged on the kingdom, routing Frederick at the White Mountain in November 1620 and replacing the regime of the estates in Bohemia with a system of “confessional absolutism” based on rigid Catholic conformity and political authoritarianism. At the same time, the Palatinate was conquered by Spanish and Bavarian troops, and the electoral title was transferred to Maximilian of Bavaria in 1623. In the Palatinate, too, the Counter-Reformation sought to bring Protestantism to an end. As the war spread into Hesse and Westphalia and as Spain resumed its attack on the Netherlands, Catholic forces seemed near triumph. This prospect, however, renewed the old fear, as in the time of Charles V, of Habsburg hegemony; an anti-Habsburg alliance was therefore forged by France (where Cardinal Richelieu took charge of affairs in 1624), England (whose ruler, James I, was father-in-law to the deposed Frederick V), the Netherlands, and Denmark (whose Protestant king, Christian IV, had extensive territorial interests in northern Germany, now threatened by Catholic armies). In 1625 Christian IV commenced hostilities. He was opposed by a much-enlarged imperial force under the war’s most flamboyant figure, Albrecht von Wallenstein, a military entrepreneur with a gift for mobilizing troops and supplying them through ruthless plundering. Wallenstein’s plan was to wreck Dutch and English commerce in the Baltic by subduing all of northern Germany and by dislodging the Swedish king, Gustav II Adolf, from Prussia (taken in the course of Sweden’s war against Poland). By 1628 much of this objective was realized. Christian IV had been decisively defeated in 1626 in the Battle of Lutter am Barenberge and forced to make peace in 1629. To crown these successes, Ferdinand II issued in March of that year the Edict of Restitution, by which Protestant rulers were to restore to the church more than 500 bishoprics, monasteries, abbeys, and other ecclesiastical properties secularized since 1552.

But this impressive strengthening of the sovereign’s power in the empire brought his foreign and domestic enemies together once more, the latter including now not only Protestants but also Roman Catholic estates concerned about their liberties. Subsidized by the Dutch and French and allied with Saxony, Sweden entered the conflict in 1630, winning commanding victories at Breitenfeld (1631) and Lützen (1632) but suffering defeat at Nördlingen in 1634. This phase of the war was marked by unprecedented brutality; for example, in 1631, imperial troops massacred two-thirds of the population of Magdeburg, a city of 20,000 that had withstood a long siege.

A way out of the long conflict appeared in 1635 when Saxony, Brandenburg, and other Protestant states seeking to end foreign intervention joined the emperor in the Peace of Prague, which included the revocation of the Edict of Restitution. But in the war’s final phase, France, seeking to forestall Spanish preponderance on the Continent, offered large subsidies to Sweden and to German princes to enable them to fight on. Combined Swedish-French campaigns commenced in 1638, and a decade later foreign armies operated as far south as Bavaria, while the French held Lorraine and Alsace, which was important to France to prevent construction of a Spanish land bridge from the Netherlands to Italy.

By then most belligerents were exhausted. Several German princes had quit the war. Since 1644, representatives of the powers had been talking about terms, although military operations continued in hopes of improving bargaining positions. In 1648, finally, treaties were signed in Münster and Osnabrück (both in Westphalia) by agents of the emperor, the German states, Sweden, and France as well as between Spain and the Netherlands. Fighting continued for some years—France and Spain did not conclude peace until 1659—but the war was at last winding down.

The Peace of Westphalia brought territorial gains to Sweden and France, awarded an electoral seat to Bavaria, and secured for Protestant rulers the church properties they had confiscated, based on the status quo of 1624. More important, it brought Calvinists into the religious settlement and established the independence of the Netherlands from Spain and of Switzerland from the empire. Most significant of all, it guaranteed the nearly unlimited territorial sovereignty of German princes, bringing to an end the last effort (until the 19th century) to centralize power in the empire. In this way the Peace of Westphalia sealed the fragmentation of the Holy Roman Empire into hundreds of autonomous political entities, most of them small. At the same time, it brought to an end the last major conflict in continental Europe in which religion was a central issue; indeed, the war itself had demonstrated that reason of state was a stronger determinant of policy than faith. In declaring the religious situation fixed as of 1624, the treaty mandated that, if a prince converted, his land no longer converted with him. Religious pluralism and—albeit grudgingly—coexistence were now the norm.

The war’s social and economic cost is difficult to gauge, modern scholarship having greatly modified original claims of vast human losses and near-total economic ruin. Nonetheless, in the most embattled realms, such as Württemberg, more than 50 percent of the people died or disappeared; elsewhere, the loss was less severe. Most historians agree that an overall population decline of 15 to 20 percent (from about 20 million to 16 or 17 million) occurred during the war and the ensuing epidemics. In addition, historians agree that in theatres of war rural impoverishment and displacement of people were widespread, while economic regression happened nearly everywhere. For German society overall, the war was a traumatic experience; it is rivaled in the national consciousness only by World War II as a time of unmitigated disaster.

To gain perspective on these calamities, their wider European aspects must be considered. Wars, uprisings, and political turmoil had occurred in many countries during the first half of the 17th century. The Fronde—a series of civil wars in France between 1648 and 1653 whose goal, at least in part, was to halt the growing power of royal government—and the Civil Wars in England (1642 to 1651) are only the most famous of these disturbances. Turmoil had occurred also in Catalonia, Portugal, Naples, Ireland, Scotland, Sweden, and Russia. Historians have referred to these events, including the numerous local manifestations of the Thirty Years’ War, as parts of a general crisis in the fabric of European society, the causes of which range from a worsening of the climate (Little Ice Age) to plagues, often spread by the armies roaming Europe almost continuously at that time. But the most destabilizing factor burdening society was the centralizing monarchy with its expanding bureaucracy, extravagant courts, swollen armies, and incessant wars, all of them supported by heavy taxation. No social group, or estate, was unaffected by the effort of monarchs to alter in their favour traditional ways of distributing power and wealth. Resentment of this and of its social cost was widespread; hence the proliferation and the scale of rebellions.