On July 28, 1914, a month after the assassination of Austrian archduke Franz Ferdinand, Austria-Hungary, the second-largest country in Europe, declared war on Serbia. Five months later after suffering a third major defeat on the battlefield, the ancient Habsburg Monarchy was left humiliated by "the peasant regiments of a small Balkan kingdom". Franz Ferdinand had not been avenged, with the Dual Monarchy losing twice as many men as the Serbs had. The blow to Habsburg prestige was incalculable and Serbia marked the first Allied victory of World War One.