Battle of Cer 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 and Danube rivers in order to prevent the Austro-Hungarians from using them during any future invasion. Belgrade was shelled
Archduke Wilhelm Franz of Austria Archduke Wilhelm Franz of Austria Archduke Wilhelm Franz Karl of Austria-Teschen (German: Erzherzog Wilhelm Franz Karl von Habsburg-Lothringen, 21 April 1827 – 29 April 1894) was an Archduke of Austria from the House of Habsburg. He was born in Vienna as the son of Archduke Charles, Duke of Teschen (1771–1847) and Princess Henrietta of Nassau-Weilburg (1797–1829). He was a grandson of Leopold II (1747–1792) and nephew of Franz II (1768–1835), the last two Holy Roman Emperors. He held the office of Grand Master of the Teutonic Knights from 1863 until his death in 1894. He gained the rank of "Feldzeugmeister"