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
Assassination of Archduke Franz Ferdinand café with the words 'Mehmedbašić who to-morrow is to be with us.'" The three sent a postcard to Black Hand Provincial Director for Bosnia-Herzegovina Vladimir Gaćinović in France. The following morning, on 28 June 1914, Ilić positioned the six assassins along the motorcade route. Ilić walked the street, exhorting the assassins to bravery. On the morning of 28 June 1914, Franz Ferdinand and his party proceeded by train from Ilidža Spa to Sarajevo. Governor Oskar Potiorek met the party at Sarajevo station. Six automobiles were waiting. By mistake, three local police officers got into the first car with the chief