The war between France, under Napoleon III, and Prussia. The war itself was provoked by Bismarck, who had skilfully isolated the French, and altered an uncontroversial message from his king (the Ems telegram). Prussian armies advanced into France; the French forces led by MacMahon were driven out of Alsace whilst a second French army was forced to retire to Metz. MacMahon, marching to relieve Metz, was comprehensively defeated by Moltke at Sedan. Napoleon was captured and, discredited in the eyes of the French, ceased to be emperor. Bismarck refused to make peace, and in September the siege of Paris began. Hopes of a French counterattack were dispelled when Bazaine surrendered at Metz and Paris finally gave way in January 1871. An armistice was granted by Bismarck, and a national assembly elected to ratify the peace, but the population of Paris refused to lay down arms and in March 1871 rose in revolt and set up the Commune of Paris. The French government signed the Treaty of Frankfurt in May and French prisoners-of-war were allowed through Prussian lines to suppress the Commune. For Prussia, the proclamation of the German Second empire at Versailles in January was the climax of Bismarck’s ambitions to unite Germany.