Franz Joseph I of Austria of his only son and heir, Crown Prince Rudolf, in 1889, and the assassination of his wife, Empress Elisabeth, in 1898. After the Austro-Prussian War, Austria-Hungary turned its attention to the Balkans, which was a hotspot of international tension because of conflicting interests with the Russian Empire. The Bosnian Crisis was a result of Franz Joseph's annexation of Bosnia and Herzegovina in 1908, which had been occupied by his troops since the Congress of Berlin (1878). On 28 June 1914, the assassination of his nephew, Archduke Franz Ferdinand, in Sarajevo resulted in Austria-Hungary's declaration of war against the Kingdom of
Archduke Ferdinand Karl of Austria the emperor's knowledge or consent, having eloped two years before the marriage was revealed publicly. On 6 August 1911 he renounced his rights and titles as a dynast of the House of Habsburg and assumed the name of "Ferdinand Burg", at the demand of Emperor Franz Joseph. Henceforth he absented himself from the Viennese court and lived in Tyrol. By then Ferdinand Karl was suffering from tuberculosis, of which he died in 1915. He and his wife had no children. Archduke Ferdinand Karl of Austria Archduke Ferdinand Karl of Austria, later known as Ferdinand Burg (Ferdinand Carl Ludwig Joseph Johann