Gravelotte-St-Privat was probably the hardest fought of all the battles of the Franco-Prussian War. Attacked by superior Prussian forces from both the First and Second armies, Marshal Bazaine's French Army of the Rhine inflicted heavy casualties on the advancing Prussian's before finally being forced to retreat into the fortress city of Metz. Unable to break out and with no hope of relief Bazaine's army grimly held on to the end of the war. French failure at Gravelotte-St-Privat led directly to their final defeat at Sedan, the collapse of Napoleon III's regime and the proclamation of the German Empire.