The Franco-Prussian War was a war between France and Prussia, which was helped by German allies of Prussia. The war was provoked by Prussian Chancellor Otto von Bismarck, who wanted to unite Germans under Prussian rule by making them fight together against a common enemy. Bismarck irritated French Emperor Napoleon III into declaring war on 19 July 1870. The war ended by a Prussian victory on 10 May 1871.