How did conflict and war lead to the construction of strong nation-states?

LLOUIS NAPOLEON PROVIDED THE OLD RULING CLASSES of Europe with a new model in politics. The question was, could this model be applied elsewhere? In Europe, the national unification of Italy and Germany offered a resounding answer. In the United States, nation building marked by sectional differences over slavery offered another.

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Garibaldi and Victor Emmanuel IIThe historic meeting in Naples between the leader of Italy’s revolutionary nationalists and the king of Sardinia sealed the unification of northern and southern Italy. With the sleeve of his red shirt showing, Garibaldi offers his hand — and his conquests — to the uniformed king and his moderate monarchical government. (Palazzo Pubblico, Siena, Italy/The Bridgeman Art Library)