In 1740 the death of the Habsburg emperor Charles VI without a male heir unleashed the most embittered conflict in Germany since the wars of Louis XIV. The question of the succession to the Austrian throne had occupied statesmen for decades. Rival claimants disputed the right—by the terms of the Pragmatic Sanction (1713)—of Charles’s daughter Maria Theresa to succeed; France supported them, its aim being, as before, the fragmentation of the Habsburg state. But it was the new Prussian king, Frederick II (1740–86), who began the conflict. To understand what follows, the modern reader should remember that few observers, even in the enlightened 18th century, disputed a ruler’s right to do what he wished with his state. Dynastic aggrandizement, territorial expansion, prestige, honour, power, and princely glory were legitimate grounds for war and sound reasons for demanding the sacrifices necessary to wage it. The only position from which to oppose this arrogation was the Christian ethic, but to do so had proved futile when last tried by Erasmus and Sir Thomas More in the 16th century. No checks—philosophical, moral, or political—therefore restrained kings from indulging their taste for conquests.

Soon after assuming power, Frederick reversed his father’s cautious policy of building and hoarding, rather than deploying, Brandenburg-Prussia’s military potential. He attacked Silesia, a province in the kingdom of Bohemia and thus part of the Habsburg monarchy, which Prussia had long desired for its populousness, mineral resources, and advanced economy. In exchange for an Austrian cession of Silesia, he offered to accept the Pragmatic Sanction (formally recognized by his predecessor in the 1728 Treaty of Berlin) and support the candidacy of Maria Theresa’s husband, Francis Stephen, as emperor. But the resolute woman who now headed the Austrian Habsburgs (1740–80) decided to defend the integrity of her realm, and the War of the Austrian Succession (1740–48; including the Silesian Wars between Prussia and Austria) began in 1740. Austria was helped only by a Hungarian army, though initial financial support came from England. Prussia was joined by Bavaria and Saxony in the empire as well as by France and Spain. The Prussian armies, though greatly outnumbered by Austria’s forces, revealed themselves as by far the best as well as the best-led. The Treaties of Dresden (1745) and Aix-la-Chapelle (1748) confirmed the Prussian conquest of Silesia. During the succeeding Seven Years’ War (1756–63), Prussian forces occupied Saxony, which had allied itself with Austria. In the Treaty of Hubertusburg of 1763, Prussia kept Silesia but could not hold on to Saxony.

In a sense, the War of the Austrian Succession was another of the many internal struggles over the constitutional balance in the empire in which territorial states opposed imperial authority. But it was also part of an international struggle, with France and England fighting out their rivalry in western and southern Europe, North America, and India. In this way it prefigured the worldwide Seven Years’ War, except that the latter followed the “diplomatic revolution” in which England switched its support from Austria to Prussia and France allied itself with its traditional foe, Austria. (A part of this agreement was the marriage, in 1770, of the Austrian princess Marie-Antoinette to the future Louis XVI.) The real significance of the Seven Years’ War lay in the Treaty of Paris of 1763, which concluded for a time the maritime and colonial conflict between France and England.

After these wars Prussia—which had increased in size and immeasurably in prestige—and Austria dominated German affairs in a condition of tension usually called “the German dualism,” meaning that each had become so powerful that only the other could keep it in some sort of check. The monarchs of both realms carried out important internal reforms. Guided by her interior minister, Count Friedrich Wilhelm Haugwitz, Maria Theresa streamlined the Austrian administrative structure on the Prussian model, thus drawing together, to the extent possible, the multiethnic and polyglot regions of the vast Habsburg empire. The remaining powers of the estates were curtailed everywhere and centralization institutionalized in absolutist fashion but without attaining the full integration of the Prussian system. Maria Theresa’s son, Joseph II (1765–90), completed this program of modernization.

In Prussia, Frederick II further tightened his control of all aspects of public life in his far-flung kingdom. However, in accordance with his personal commitment to rational tolerance and free-thinking skepticism, he also undertook extensive legal reforms. He virtually abolished judicial torture, lifted some of the tax burden from the poorest of his subjects, established religious tolerance as a policy of his state, and encouraged scientific and scholarly activity in the Prussian Academy of the Sciences. Like his father, he was a vigorous promoter of economic development. His taste for French Enlightenment thought and his own prolific creativity in letters and music lent his reign the flavour of an era shaped by a philosopher-king, albeit one with the instincts of a ruthless power politician. His successes in war and peace earned him a place as national hero as well as the title “the Great.”