SMS Arminius  was an ironclad warship of the Prussian Navy, later the Imperial German Navy. The vessel was a turret ship that was designed by the British Royal Navy Captain Cowper Coles and built by the Samuda Brothers shipyard in Cubitt Town, London as a speculative effort; Prussia purchased the ship during the Second Schleswig War against Denmark, though the vessel was not delivered until after the war. The ship was armed with four 21 cm (8.3 in) guns in a pair of revolving gun turrets amidships. She was named for Arminius, the victor of the Battle of the Teutoburg Forest.

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.