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
Muhamed Mehmedbašić the way to Sarajevo, gendarmes searched the train; fearing they were on to him, he threw the knife out the window. Potiorek was planned to be assassinated at the end of March 1914, when the new mufti Čaušević was to be enthroned in Sarajevo. However, upon hearing that Archduke Franz Ferdinand of Austria would come to Sarajevo on Vidovdan, the Black Hand changed their minds. The Archduke's scheduled visit on Vidovdan (28 June), a Serbian national holiday, was perceived as an insult. Ilić summoned Mehmedbašić and informed him on 26 March that the plan now was to murder Archduke Franz