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 Viktor of Austria-Este Archduke Ferdinand Karl Viktor of Austria-Este Ferdinand Karl Viktor (20 July 1821 – 15 December 1849) was Archduke of Austria-Este and Prince of Modena. Born in Modena, he was the second son of Francis IV of Modena and his niece-consort Maria Beatrice of Savoy. His paternal grandmother had been heiress to the Duchy of Modena, because her father Ercole III d'Este had no sons. Ferdinand married Archduchess Elisabeth Franziska of Austria, daughter of Archduke Josef Anton of Austria and his third wife Duchess Maria Dorothea of Württemberg on 4 December 1846 in the Schönbrunn Palace in Vienna. Elisabeth and Ferdinand