Battle of Cer On 28 June 1914, Bosnian Serb student Gavrilo Princip assassinated Archduke Franz Ferdinand of Austria in Sarajevo. The assassination precipitated the July Crisis, which led Austria-Hungary to issue an ultimatum to Serbia on 23 July on suspicion that the assassination had been planned in Belgrade. The Austro-Hungarian government made the ultimatum intentionally unacceptable to Serbia, and it was indeed rejected. The Austro-Hungarians declared war on Serbia on 28 July and that same day the Serbs destroyed all bridges on the Sava and Danube rivers in order to prevent the Austro-Hungarians from using them during any future invasion. Belgrade was shelled
Archduchess Elisabeth Amalie of Austria Saxony, he had no children. With his second wife Princess Maria Annunciata of Bourbon-Two Sicilies, Karl Ludwig fathered Archduke Franz Ferdinand of Austria, who became heir to the throne of Austria-Hungary, as well as three other siblings. Elisabeth and her older sister Archduchess Maria Annunziata of Austria (later Abbess of the Theresia Convent in the Hradschin, Prague) were the product of his third marriage to Infanta Maria Theresa of Portugal, a daughter of the deposed King Miguel I of Portugal. In addition, her father was a younger brother of Franz Joseph I of Austria, the reigning emperor at the time