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
Russian entry into World War I of Austria of Germany and the Austro-Hungarian Empire. The consensus of scholars includes scant mention of Russia, and briefly mentions Russia's defense of Orthodox Serbia, its pan-Slavic roles, its treaty obligations with France, and its concern for protecting it status as a great power. The Archduke Franz Ferdinand of Austro-Hungary was assassinated by Bosnian Serbs on 28 June 1914 to protest Austrian takeover of a largely Slavic province. Vienna was unable to find evidence that Serbia had sponsored the assassination but a month later issued an ultimatum to Serbia, which it knew would be rejected and thus lead to war.