The Franco-Prussian War (July 19, 1870 – May 10, 1871) was declared by France on Prussia which was backed by the North German Confederation. The south German states of Baden, Württemberg and Bavaria joined in on the side of Prussia. The conflict marked the culmination of tension between the two powers following Prussia's rise to dominance in Germany, before 1866 still a loose federation of quasi-independent territories.
The war began over the possible ascension of a candidate from Prussia's Hohenzollern royal family to the vacant Spanish throne as Isabella II had abdicated in 1868 -- therefore, the war could technically be known as the Second War of Spanish Succession. This was strongly opposed by France who issued an ultimatum to King Wilhelm I of Prussia to have the candidacy withdrawn, which was done. Aiming to humiliate Prussia, Emperor Napoleon III of France then required Wilhelm to apologize and renounce any possible further Hohenzollern candidature to the Spanish throne. King Wilhelm, surprised at his holiday resort by the French ambassador, declined as he was not informed yet. Prussia's prime minister Otto von Bismarck edited the king's account of his meeting with the French ambassador to a shortened and cutting version, and authorizing its release to the press and embassies, as the famous Ems Dispatch.
The French people and their parliament reacted with outrage, Napoleon III mobilized and declared war, on Prussia only, but effectively also on the states of southern Germany. The German armies quickly mobilized and within a few weeks controlled large amounts of land in Eastern France. Their success was due in part to rapid mobilization by train, one of the first times a nation effectively used railroads to mobilize an army for war, to Prussian General staff leadership and to modern Krupp artillery made of steel. Napoleon III was captured with his whole army at the Battle of Sedan, yet this did not end the war, as a republic was declared in Paris on 4 September 1870, marking the creation of the Third Republic of France under the Government of National Defense and later the "Versaillais government" of Adolphe Thiers. The immediate result was an extension to the war as the Republic proclaimed a continuation of the fights.
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