The Franco-Prussian War or Franco-German War (German: Deutsch-Französischer Krieg, lit. German-French War, French: Guerre franco-allemande, lit. Franco-German War), often referred to in France as the War of 1870 (19 July 1870 – 10 May 1871), was a conflict between the Second French Empire 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. Some historians argue that the Prussian chancellor Otto von Bismarck planned to provoke a French attack in order to draw the 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.