After a period of constitutional deadlock between crown and parliament in Prussia, a crisis arose in 1863 over the duchies of Schleswig and Holstein, disputed between Denmark and the German Confederation. After the Danish annexation of Schleswig, Otto von Bismarck, the new prime Minister of Prussia, made the smaller states of the German Confederation join Prussia and Austria in the war with Denmark. The Second Schleswig War ended with the defeat of the Danes at Dybbøl, and an agreement between Austria and Prussia to jointly administer Schleswig and Holstein.
Bismarck then set about making Prussia the undisputed master of northern Germany, weakening Austria and the German Confederation. This eventually led to a German civil war, the Austro-Prussian War, in which in the Battle of Langensalza (the last battle between Germanic states on German soil) Hanover won a victory, but was so weakened by it, that it could offer no resistance to the occupation by Prussia and ceased to be an independent state. The victory of Prussia and its allies at Königgrätz in July 1866, against Austria and its allies sealed this. The result was the dissolution of the German Confederation, and the creation of the North German Confederation one year later.
The Prussian 7th Cuirassiers charge the French guns at the Battle of Mars-La-Tour, August 16, 1870
Bismarck wanted a war with France to unify the German peoples, and French Emperor Napoleon III, unaware of his military weakness, provided the Franco-Prussian War of 1870–71, expecting support from Prussias recent enemies. Unlike in the war only a few years ago, the Germans turned not against each other, with the first emergence of a strong German national sentiment in the background. Instead, the southern German monarchs of Bavaria, Württemberg, and Baden honoured their secretly negotiated treaties of mutual defence with Berlin, while Austria remained neutral.
The Germans, led by King William I of Prussia and Moltke the Elder, mobilized a mass con army of 1.2 million men (300,000 regulars and 900,000 reserves and Landwehr) which faced 492,585 experienced regular French soldiers and 420,000 Garde Mobile under Napoleon III of France. Within the first month of war the German army encircled big French armies, at Gravelotte, Metz, and Sedan and destroyed them. The war culminated with the defeat of the French army during the Siege of Paris, and was followed by the proclamation of the German Empire in 1871.