Battle of Kolubara their respective commands, and the 5th and 6th armies were merged into a single 5th Army of 95,000 men. 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
Archduke Franz Ferdinand of Austria Duke of Teschen. Franz began to visit Archduke Friedrich's villa in Pressburg (now Bratislava), and in turn Sophie wrote to Franz Ferdinand during his convalescence from tuberculosis on the island of Lošinj in the Adriatic. They kept their relationship a secret, until it was discovered by Isabella herself. To be eligible to marry a member of the imperial House of Habsburg, one had to be a member of one of the reigning or formerly reigning dynasties of Europe. The Choteks were not one of these families, although they did include among their ancestors, in the female line, princes of Baden,