Political map of Europe & the Mediterranean 01 September 1870 (Outbreak of the Franco-Prussian War): In 1870 a Prussian prince (Leopold, Prince of Hohenzollern) accepted the Spanish throne. Outraged, the French made the prince back down, then tried to pressure the King of Prussia (William I of Prussia) to never permit a Spanish candidacy. Bismarck (Otto von Bismarck) immediately released this discussion (Ems Dispatch) to the press, carefully editing it to inflame both sides. The French declared war (Franco-Prussian War) but the Prussians were better organized, surrounding and defeating Napoleon III's (Napoleon III) army at Sedan (Battle of Sedan (1870)).