Harsh economic conditions in the seventeenth century were greatly exacerbated by the decades-long conflict known as the Thirty Years’ War (1618–1648). Shifts in the balance between the population of Protestants and Catholics in the Holy Roman Empire led to the deterioration of the Peace of Augsburg. Lutheran princes felt compelled to form the Protestant Union (1608), and Catholics retaliated with the Catholic League (1609). Dynastic interests were also involved; the Spanish Habsburgs strongly supported the goals of their Austrian relatives: the unity of the empire and the preservation of Catholicism within it.

The war began with a conflict in Bohemia (part of the present-day Czech Republic) between the Catholic League and the Protestant Union but soon spread through the Holy Roman Empire, drawing in combatants from across Europe. After a series of initial Catholic victories, the tide of the conflict turned due to the intervention of Sweden, under its king Gustavus Adolphus (r. 1594–1632), and then France, whose prime minister, Cardinal Richelieu, intervened on the side of the Protestants to undermine Habsburg power.

The 1648 Peace of Westphalia that ended the Thirty Years’ War marked a turning point in European history. The treaties that established the peace not only ended conflicts fought over religious faith but also recognized the independent authority of more than three hundred German princes (Map 18.2), reconfirming the emperor’s severely limited authority. The Augsburg agreement of 1555 became permanent, adding Calvinism to Catholicism and Lutheranism as legally permissible creeds. The United Provinces of the Netherlands, known as the Dutch Republic, won official freedom from Spain.

The Thirty Years’ War was probably the most destructive event in central Europe prior to the world wars of the twentieth century. Perhaps one-third of urban residents and two-fifths of the rural population died.