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 Joseph Franz of Austria Archduke Joseph Franz of Austria Archduke Joseph Franz Leopold of Austria (9 April 1799 – 30 June 1807) was the second son and seventh child of Francis II, the last Holy Roman Emperor and his second wife, Maria Theresa of Naples and Sicily, daughter of Ferdinand I of the Two Sicilies and his wife Maria Carolina of Austria. He was their fourth child to die. Archduke Joseph Franz was born at the Hofburg Imperial Palace, where all of his older and younger siblings were born. He was the seventh child born to his parents: Marie Louise was born in 1791,