Despite their success in state-building, Prussia's rulers had an acute sense of contingency. Lacking natural, defensible frontiers, their realm was a political construct that demanded effort to sustain. Clark describes vulnerability as an abiding theme-and central problem-in Prussian history. Geopolitics meant that Prussia could not avoid being drawn into European wars. Ambition made the problem worse when Frederick II's annexation of Silesia sparked what became a war to partition Prussia. As Britain's ally during the Seven Years War, Prussia faced the armies of France, Austria and Russia almost alone. While Prussia survived, Frederick the Great later described the war as "not a game to play often."

WITH NAPOLEON, Prussia played the game and lost. Defeat in 1806 made it a French satellite but also prompted a wave of reform, culminating in the war of liberation following Napoleon's defeat in Russia. Changes in executive government streamlined decision-making and gave ministers greater power in dealing with the king. The state became separate from the Hohenzollerns, attracting a loyalty of its own. Military innovations raised effectiveness while aiming to make the army the repository of a virtuous patriotism, and professionalizing military planning through a general staff had long-term consequences. Educational reforms also contributed to the emergence of citizenship while setting a model for modern schools and universities.

The early 19th century marked a high point characterized by learning, culture and economic growth. Prussia had a model civil administration and legal system. If Britain was a more liberal polity, the administration of justice and number of death sentences suggest that Prussia was far more humane. At the Congress of Vienna it gained valuable territory along the Rhine that laid the foundation for subsequent industrialization. As part of the overall post-1815 European settlement, Prussia and Austria shared responsibility for leading Germany. While Prussia took an ambivalent view of German nationalism-its king refused the offer of a crown in 1848 by the Frankfurt Parliament-it eventually clashed with Austria. Conceptions of German unity shifted from the cultural unity of the medieval reich, which encompassed independent rulers, toward the different concept of the nation-state. When Austria forced its Prussian rival to back down from its efforts to unify Germany in the aftermath of the 1848 revolutions, Otto von Bismarck later used several wars to bring Germany together under its sole leadership. Bismarck cut an ambivalent figure. Although a nobleman with an attitude to match, he had a bourgeois education and intellectual bent that drew him apart from the landed aristocracy as a class. Like many Prussian nobles, he sought fulfillment in serving the state, but Clark describes him as serving without being a servant. Bismarck pushed through policies against the monarch's will, and he later displayed contempt for both public opinion and rival centers of power. His eye for the ripe moment, and a sense of when to pull back, made him the architect of German unification.

What Benjamin Disraeli called the German revolution-"a greater political event than the French"-profoundly changed Europe. After unification, Bismarck constructed a network of alliances designed to sustain a favorable international order for what had become a satisfied power. Isolating France and entangling Russia and Austria in alliances worked for a time, but Bismarck's system required Bismarck or someone equally shrewd to manage it. Once William II "dropped the pilot"-as the famous 1890 Punch cartoon by Sir John Tenniel depicted Bismarck's dismissal-the system broke down into rival alliance blocks that left Germany almost isolated.

Dropping the pilot offers a good metaphor for Prussia's absorption into a Germany that found itself adrift in an increasingly unstable world. Bismarck's reich was a highly artificial product of war and diplomacy, and a fearful and reactive tone emerged from the realization that what had been constructed could be deconstructed. The crown and administration had lost control in 1848, and authorities refused to risk a reprise. Reactions to perceived threats demonstrated brittleness rather than strength. The anti-clerical Kulturkampf failed to break Catholic political influence and only showed the limits of state authority. An increasingly strident view of Slavs marked a new defensiveness. With the growth of socialism, German politics became further polarized along confessional and class lines.

Religion no longer provided a stabilizing force. Michael Burleigh has shown how the Protestant middle classes in Germany, for instance, distanced themselves from their churches, viewing traditional religious observance as the remnant of a discredited past. Science and culture, along with militant nationalism, filled the role religion had once played. Pursuit of power replaced the fulfillment of duty as the lodestar guiding public culture.

With consensus increasingly elusive, German leaders used tough stands on foreign issues to divert attention from domestic tensions. If foreign threats rallied support, they also fed the crisis mentality that encouraged erratic actions. The flucht nach vorn ("flight to the front") under William II landed Germany in conflicts with other powers. Encirclement was a Prussian nightmare that became Germany's reality and attempting to solve the problem through a quick war in 1914 brought catastrophe.

World War I corroded Prussian institutions and identity, furthering its absorption into Germany. The Junker class lampooned by satirists had drifted from its roots. Rather than a product of older Prussian virtues, men like Paul von Hindenburg reflected the new Germany's flexible power politics. Like many among the German political elite, Hindenburg was an opportunist who carelessly rolled the dice with Germany's future and lost badly.

Instability following defeat in 1918 left German society open to extremes, and later unrest brought Hitler to power. Nazi efforts to appropriate Prussia's legacy show betrayal in the name of the thing being betrayed. Elite responses were mixed, with some nobles trying to secure established authority in a new system by party membership and others choosing resistance to a regime that offended their values. As the Prussian idea became increasingly abstract and desiccated, competing groups treated it as a blank page on which they could impose their own meanings. The image lingered well after the substance had decayed. Prussian history marks a cautionary tale of hubris leading to nemesis. Like the famous words of Kipling and Shelley, it warns how the mighty fall.

William Anthony Hay is a professor of history at Mississippi State University and co-author with Harvey Sicherman of Is There Still a West? The Future of the Atlantic Alliance (University of Missouri Press, 2007).