Modern History/Franco-Prussian War

The Franco-Prussian War (July 19, 1870 – May 10, 1871) was fought between France and Prussia (backed by the North German Confederation and the southern German states of Baden, Bavaria and Württemberg). The conflict marked the culmination of rising tensions between the two powers following Prussia's increasing dominance in Germany, then still a loose federation of quasi-independent territories.

Origins
The long term causes of the war can be traced back decades. France was understandably anxious about the increasing economic and political power of Prussia to its east, and at the same time eager to pursue it's old diplomatic aims of the expansion of its territories eastwards. Internally, the Bonapartist regime that ruled France faced increasing dissent, and some believed that a successful war against Prussia would not only provide economic and territorial gains but also prevent revolution. Prussia, on the other hand, believed that a war with France would help strengthen Germany as a whole by ending French influence, and that a victorious Prussia could achieve the ultimate goal of the unification of Germany. These tensions increased due to a number of diplomatic crises between the two nations in the 1860s, particularly over the Austro-Prussian War and France's attempt to purchase Luxembourg.

The war was finally triggered by a dispute over the possible ascension of the German Prince Leopold of Hohenzollern-Sigmaringen (a member of Prussia's Hohenzollern royal family) to the Spanish throne, following the abdication of Isabella II in 1868. The French government feared that this expansion of Prussian influence would weaken France's position in Europe, not least because it made it probable that any war with Prussia would lead to war with Spain, forcing France to fight on two fronts. The French Emperor Napoleon III issued an ultimatum to the Prussian King Wilhelm I demanding that Leopold be withdrawn from candidacy for the Spanish throne, and he complied. Eager to press their perceived advantage, the French demanded a guarantee that no other Hohenzollern candidates would be put forwards, but the Prussian government refused. French public opinion was inflamed, and France declared war.

The War
There were many European nations which had motives to go to war against Prussia alongside France, but Napoleon III's mismanagement of France's foreign policy had led to the diplomatic isolation of France, and at the outbreak of war France was unable to find any allies. In contrast, Prussia had signed treaties with the southern German states of Baden, Bavaria and Württemberg which guaranteed their support if war was declared against Prussia.

France was able straight away to field an army of about 400,000 highly trained soldiers, compared to roughly 1.2 million Prussian and southern German troops. However, the German soldiers were not regulars and would take some time to train, so the French army had an initial advantage. This was exploited by pushing forwards up to the German border, and on August 2 the French seized the city of Saarbrücken. The Prussian army moved swiftly against them, and less than a week after Saarbrücken fell, the German forces inflicted a series of heavy defeats upon the French. The Prussian army steamrollered it's way into France, capturing Metz in October after a bloody siege. Although Napoleon III himself surrendered and was taken prisoner following the Battle of Sedan in early September, the war continued to be fought by a French republican government for several months.