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 Peter Ferdinand of Austria Archduke Peter Ferdinand of Austria Archduke "Peter Ferdinand" Salvator Karl Ludwig Maria Joseph Leopold Anton Rupert Pius Pancraz of Austria, Prince of Hungary and Bohemia, Prince of Tuscany) (12 May 1874, Salzburg, Austria-Hungary – 8 November 1948, St. Gilgen, Salzburg, Austria) was an Austro-Hungarian archduke and an army commander in the Austro-Hungarian Army during World War I. He was also the titular Grand Duke of Tuscany from 2 May 1921 to 8 November 1948. Peter Ferdinand was the fourth child and third-eldest son of Ferdinand IV, Grand Duke of Tuscany and his wife Alice of Bourbon-Parma. His two elder brothers