Franco-Prussian relations only got worse, until 1868, over the issue of a Hohenzollern candidate for the Spanish throne. The public release of the Ems Dispatch, which showed “insults” between the Prussian king and the French ambassador, inflamed public opinion in France and Germany; part of the event was engineered by the Prussian Chancellor Bismarck.
In 1870, France mobilized and declared war on Prussia only, but other German states quickly joined on Prussia's side.
Prussia had better Krupp steel artillery and had the fourth densest rail network in the world at the time. France, however, only had the fifth densest rail network.
The Battle of Sedan resulted in Napoleon III and his army being captured on September 2, because the German troops had penetrated the area with swiftness and surrounded his army - the same German tactics used in the Blitzkrieg of World War II.
The Third Republic was declared in Paris on September 4, 1870 and French resistance continued. Over a five month campaign, the German forces defeated the newly recruited French armies in a series of battles fought across northern France.
Ten days before the fall of Paris, the German states proclaimed their union as the German Empire under the Prussian king, Wilhelm I, uniting Germany as a nation-state, changing the history of Germany forever.
Following a prolonged siege, noted for the first use of anti-air artillery, Paris fell on 28 January 1871.
The final Treaty of Frankfurt was signed 10 May 1871. The settlement gave Germany the French territories of Alsace and part of Lorraine.
The Franco-Prussian War was the most important war fought in Europe after the Napoleonic Wars but before the First World War. The most important consequence was the unification of Germany into an empire in its own right. However, imperialist ambitions of these countries would spur further conflicts, as France’s determination to regain Alsace-Lorraine would lead to World War I.