World War I and beyond. On 28 June 1914, Archduke Franz Ferdinand, heir presumptive to the Austro-Hungarian Empire, visited the Bosnian capital, Sarajevo. A group of six assassins (Cvjetko Popović, Gavrilo Princip, Muhamed Mehmedbašić, Nedeljko Čabrinović, Trifko Grabež, and Vaso Čubrilović) from the Yugoslavist group Mlada Bosna, supplied with arms by the Serbian Black Hand, gathered on the street where the Archduke's motorcade was to pass, with the intention of assassinating him. The political objective of the assassination was to break off Austria-Hungary's South Slav provinces, which Austria-Hungary had annexated from the Ottoman Empire, so they could be combined into a Yugoslavia. Čabrinović
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