Anton von Werner's painting of the proclamation of the German Empire in the Hall of Mirrors at Versailles, January 18, 1871.

In 1807, Prussia nearly ceased to exist. Napoleon had annihilated its famous army at Jena and Auerstedt, occupied Berlin, and imposed a peace that stripped away half its territory and capped its army at 42,000 men. Sixty-four years later, a Prussian king was proclaimed German Emperor in the Hall of Mirrors at Versailles — the palace of the French kings. How a broken medium-sized kingdom became the master of continental Europe is one of the most consequential stories of the modern age.

The transformation began, paradoxically, with the humiliation itself. A generation of reformers — Stein, Hardenberg, Scharnhorst, Gneisenau — concluded that Prussia had lost not to French genius but to its own fossilized institutions. In less than a decade they abolished serfdom, opened the officer corps to talent rather than birth, and created something no other country had: a permanent general staff, a body of professionally trained planners who studied war in peacetime. The army cap imposed by Napoleon even helped — Prussia trained conscripts in short rotations, quietly building a large trained reserve behind a small legal army.

At the Congress of Vienna in 1815, the victors handed Prussia the Rhineland, largely to keep a watchful garrison near France. It looked like a burden: distant, Catholic, culturally alien to Protestant Berlin. It turned out to contain the Ruhr valley — the richest coal and iron region in Europe, and the future engine of German industry. Few territorial awards in history have paid out so spectacularly by accident.

The next weapon was economic. In 1834 Prussia organized the Zollverein, a customs union that eventually embraced most German states — and pointedly excluded Austria, the other claimant to German leadership. For three decades before a single shot was fired, German trade, railways and industrial standards were being quietly organized from Berlin.

There was one path to unification Prussia pointedly refused. In 1849, the Frankfurt Parliament — the liberal assembly thrown up by the revolutions of 1848 — offered Frederick William IV the crown of a united, constitutional Germany. He turned it down, sneering privately that he would not accept a "crown from the gutter." Germany would not be united by parliaments and speeches. When unification came, it would arrive by the only route the Prussian state respected: as the reformers' army and the Zollverein's railways, directed by a single ruthless intelligence.

That intelligence was Otto von Bismarck, appointed minister-president in 1862 over the furious objections of the liberal parliament. "The great questions of the day," he announced in his first week, "will not be decided by speeches and majority resolutions — but by iron and blood." There followed the famous trilogy of short, decisive wars. Denmark in 1864 yielded Schleswig-Holstein. Austria in 1866 was beaten in seven weeks — the general staff's railways and needle-guns delivering exactly what they had been designed for — and was expelled from German affairs entirely. France in 1870–71 was the final act: the French army was encircled at Sedan, Napoleon III captured, and Paris besieged. The southern German states, swept up in the national moment, joined the Prussian-led federation. On January 18, 1871, in a hall built to glorify Louis XIV, the German Empire was proclaimed.

Contemporaries grasped what had happened. Mirabeau's old quip — that Prussia was not a state with an army but an army with a state — had come true at continental scale, but with a modern twist: the army now ran on coal, telegraph lines and timetables. In 1866, Prussian corps converged on the Austrians at Königgrätz by five separate railway lines, a feat of coordination no other power could have attempted. The battle involved nearly half a million men, the largest European battle of the century, and it was decided as much in the planning offices of Berlin as on the field.

The map of Prussia's growth — from the truncated state of 1807, through the gains of 1815, to the empire of 1871 — is really a map of a new kind of power: railways, coal, schoolteachers and staff officers substituting for glory and dynastic prestige. Europe's other powers understood the lesson perfectly, and spent the next four decades copying the Prussian model of universal conscription and professional planning. The continent-wide arms race that followed ended in August 1914 — which is another story, and another map.

Sources: Christopher Clark, Iron Kingdom: The Rise and Downfall of Prussia; James Sheehan, German History 1770–1866; Encyclopaedia Britannica, "Franco-German War" and "Zollverein"; Geoffrey Wawro, The Austro-Prussian War.

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