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 Ferdinand Karl Joseph of Austria-Este Archduke Ferdinand Karl Joseph of Austria-Este Archduke Ferdinand Karl Joseph of Austria-Este (25 April 1781 – 5 November 1850) was the third son of Archduke Ferdinand of Austria-Este and of his wife Princess Maria Beatrice Ricciarda d'Este, last member and heiress of the House of Este. For much of the Napoleonic Wars he was in command of the Austrian army. Ferdinand was born at Milan. He attended the military academy in Wiener Neustadt before embarking on a military career. In 1805 in the war of the Third Coalition against France, Ferdinand was commander-in-chief of the Austrian forces with General Karl