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
Austria–Germany relations in this unified Germany. Austria-Hungary then turned its imperial ambitions to the Balkan Peninsula; whereas the German Empire focused on building armaments in a race against the United Kingdom (Britain and Ireland). Nevertheless, both the German Empire and Austria-Hungary forged a military alliance with the Kingdom of Italy, forming the Triple Alliance (1882). In the 1910s, Austria-Hungary's ambition of turning Serbia into its protectorate facilitated the Assassination of Archduke Franz Ferdinand (1914), heir to Austria-Hungary's throne. When Austria-Hungary stirred up excuses for a war (First World War) against Serbia, Germany, claiming the Alliance's terms of passive military defence instead of