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
SMS Kaiser Karl VI and Argentina. On 25 May, she represented Austria-Hungary at the centennial of Argentina's May Revolution, which won the country's independence from Spain. On 28 June 1914, Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, was assassinated in Sarajevo; the assassination sparked the July Crisis and ultimately the First World War, which broke out a month later on 28 July. The German battlecruiser , which had been assigned to the Mediterranean Division, sought the protection of the Austro-Hungarian fleet, and so Admiral Anton Haus sent the fleet, including "Kaiser Karl VI", south on 7 August to assist his German ally.