The Franco-Prussian War or Franco-German War, often referred to in France as the War of 1870 or in Germany as 70/71, was a conflict between the Second French Empire of Napoleon III and the German states of the North German Confederation led by the Kingdom of Prussia. The conflict was caused by Prussian ambitions to extend German unification and French fears of the shift in the European balance of power that would result if the Prussians succeeded. Some historians argue that the Prussian chancellor Otto von Bismarck deliberately provoked a French attack in order to draw the independent southern German states—Baden, Württemberg, Bavaria and Hesse-Darmstadt—into an alliance with the North German Confederation dominated by Prussia, while others contend that Bismarck did not plan anything and merely exploited the circumstances as they unfolded. None, however, dispute the fact that Bismarck must have recognized the potential for new German alliances, given the situation as a whole.
On 16 July 1870, the French parliament voted to declare war on the German Kingdom of Prussia and hostilities began three days later.