The Franco-Prussian War or Franco-German War, often referred to in France as the War of 1870, was a conflict between the Second French Empire and the North German Confederation led by the Kingdom of Prussia. Lasting from 19 July 1870 to 28 January 1871, the conflict was caused primarily by France's determination to reassert its dominant position in continental Europe, which appeared in question following the decisive Prussian victory over Austria in 1866. According to some historians, Prussian chancellor Otto von Bismarck deliberately provoked the French into declaring war on Prussia in order to induce four independent southern German states—Baden, Württemberg, Bavaria and Hesse-Darmstadt—to join the North German Confederation; other historians contend that Bismarck exploited the circumstances as they unfolded. All agree that Bismarck recognized the potential for new German alliances, given the situation as a whole.

The Kingdom of Prussia constituted the German state of Prussia between 1701 and 1918. It was the driving force behind the unification of Germany in 1866 and was the leading state of the German Empire until its dissolution in 1918. Although it took its name from the region called Prussia, it was based in the Margraviate of Brandenburg. Its capital was Berlin.