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
Charles I of Austria Charles I of Austria Charles I or Karl I (Karl Franz Joseph Ludwig Hubert Georg Otto Maria; 17 August 18871 April 1922) was the last Emperor of Austria, the last King of Hungary (as Charles IV, ), the last King of Bohemia (as Charles III), and the last monarch belonging to the House of Habsburg-Lorraine. After his uncle Archduke Franz Ferdinand of Austria was assassinated in 1914, Charles became heir presumptive of Emperor Franz Josef. Charles I reigned from 1916 until 1918, when he "renounced participation" in state affairs, but did not abdicate. He spent the remaining years of his