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
Sophie, Duchess of Hohenberg and Archduke Franz Ferdinand. Through her grandmother's family, the Berchtolds, she is distantly related to former Austro-Hungarian foreign minister Count Leopold Berchtold and to Austrian conductor Nikolaus Harnoncourt. Cardinal Christoph Schönborn is a great-grandson of her niece, Marie Chotek. Sophie, Duchess of Hohenberg Sophie, Duchess of Hohenberg (; ; 1 March 1868 – 28 June 1914), was the wife of Archduke Franz Ferdinand of Austria, the heir to the Austro-Hungarian throne. Their assassination in Sarajevo sparked a series of events that eventually led to World War I. Sophie was born in Stuttgart as the fourth daughter of Count Bohuslav Chotek