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 Otto of Austria (1865–1906) to repair their relationship with the Saxon royal family, after both Crown Prince Rudolf and Otto's brother Franz Ferdinand had snubbed the Saxons by rejecting Maria's elder sister Mathilde. Otto and Maria had two sons: Their marriage was unhappy, however, since the Archduke was often unfaithful. He had two children by his mistress, Marie Schleinzer: The mountain lodge on the Rax plateau in Lower Austria, is named after him. Archduke Otto of Austria (1865–1906) Otto Franz Joseph Karl Ludwig Maria, Prince Imperial and Archduke of Austria, Prince Royal of Hungary and Bohemia (21 April 1865 – 1 November 1906) was