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 Karl Ferdinand of Austria He became a Lieutenant Field Marshal of the Austrian Army. In Vienna, on 18 April 1854, Karl Ferdinand married his first cousin, Archduchess Elisabeth of Austria (1831–1903), the widow of Archduke Ferdinand of Austria-Este, and the daughter of Archduke Joseph of Austria, Palatine of Hungary. They had six children: Archduke Karl Ferdinand of Austria Archduke Karl Ferdinand of Austria (Vienna, 29 July 1818 – Gross Seelowitz (Židlochovice Castle), 20 November 1874) was the second son of Archduke Charles, Duke of Teschen (1771–1847) and Princess Henrietta of Nassau-Weilburg, and the maternal grandfather of King Alfonso XIII of Spain. A son of