 Despite the restoration of the previous order with the 1815 Congress of Vienna, the "nationalities question" became the main problem of Europe during the Industrial Era, leading in particular to the 1848 Revolutions, the Italian unification completed during the 1871 Franco-Prussian War, which itself culminated in the proclamation of the German Empire in the Hall of Mirrors in the Palace of Versailles, thus achieving the German unification.Meanwhile, the Ottoman Empire, the "sick man of Europe", was confronted with endless nationalist movements, which, along with the dissolving of the Austrian-Hungarian Empire, would lead to the creation, after World War I, of the various nation-states of the Balkans, with "national minorities" in their borders.Ethnic nationalism, which advocated the belief in a hereditary membership of the nation, made its appearance in the historical context surrounding the creation of the modern nation-states.