Which country unified under Bismarck in 1871?

Germany, proclaimed in the Hall of Mirrors at Versailles - in a defeated France, deliberately, which is the sort of detail that produces consequences. Fifty years later the treaty ending the First World War was signed in the same room, which was equally deliberate.

Bismarck built it with three short wars in seven years, each chosen for a specific political result rather than for territory: against Denmark in 1864, Austria in 1866 to exclude it from German affairs, and France in 1870 to give the southern German states a reason to join. He also edited a telegram to make it read as an insult, which is what got France to declare war and therefore look like the aggressor.

Having built it he spent the rest of his career trying to stop it growing, on the grounds that a united Germany was already big enough to frighten everyone and needed to look harmless. He also introduced state pensions, health insurance and accident insurance in the 1880s - the first welfare state anywhere - explicitly to undercut the socialists rather than out of sympathy. He was dismissed in 1890 by a young Kaiser who wanted a more ambitious foreign policy, which is roughly where the road to 1914 begins.