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The formal unification of Germany into a politically and administratively integrated nation state officially occurred on 18 January 1871 at the Versailles Palace's Hall of Mirrors in France. Princes of the German states gathered there to proclaim Wilhelm of Prussia as Emperor Wilhelm of the German Empire after the French capitulation in the Franco-Prussian War. Unofficially, the transition of most of the German-speaking populations into a federated organization of states occurred over nearly a century of experimentation. Unification exposed several glaring religious, linguistic, social, and cultural differences between and among the inhabitants of the new nation, suggesting that 1871 only represents one moment in a continuum of the larger unification processes.
The model of diplomatic spheres of influence resulting from the Congress of Vienna in 1814–15 after the Napoleonic Wars endorsed Austrian dominance in Central Europe. However, the negotiators at Vienna took no account of Prussia's growing strength within and among the German states, failing to foresee that Prussia would challenge Austria for leadership within the German states. This German dualism presented two solutions to the problem of unification: Kleindeutsche Lösung, the small Germany solution (Germany without Austria), or Großdeutsche Lösung, greater Germany solution (Germany with Austria). Reaction to Danish and French nationalism provided foci for expressions of German unity. Military successes—especially Prussian ones—in three regional wars generated enthusiasm and pride that politicians could harness to promote unification. This experience echoed the memory of mutual accomplishment in the Napoleonic Wars, particularly in the War of Liberation of 1813–14. By establishing a Germany without Austria, the political and administrative unification in 1871 at least temporarily solved the problem of dualism.