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
Russian entry into World War I was in agreement with President minister Raymond Poincaré who trusted him. He promised unconditional French support to Russia in the unfolding crisis with Germany and Austria. Historians debate whether he exceeded his instructions but they agree he failed to inform Paris of exactly what was happening, and did not warn that Russian mobilization might launch a world war. When on 28 June 1914 Archduke Franz Ferdinand of Austria was assassinated in Sarajevo Tsar Nicholas vacillated as to Russia's course of action. A relatively new factor influencing Russian policy was the growth of the Pan-Slavism spirit that identified Russia's duty to