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
French entry into World War I was not sincere in seeking peace. The French consensus was that war was inevitable. The war arose from conflict between two alliances: the Triple Alliance of Germany, Austria and Italy, and the Triple Entente of France, Russia and Britain. France had had a military alliance with Russia since 1894, designed primarily to neutralize the German threat to both countries. Germany had a military alliance with Austria-Hungary. In June 1914, Archduke Franz Ferdinand, the heir to the Austrian throne, was assassinated. The government of Austria decided to destroy Serbia once and for all, for stirring up trouble among ethnic Slavs. Berlin