The assassination of Archduke Franz Ferdinand, heir prince of the Austro-Hungarian Empire in Sarajevo by Serbian extremists, on June 28, 1914. This prompted Emperor Franz Joseph of Austria-Hungary to send an ultimatum to the government of Serbia. As the terms presented in the ultimatum could not be met by the Serbians, Austria-Hungary declared war on Serbia, a political action that triggered the system of alliances of the major European powers in a domino effect: after Austria-Hungary declared war on Serbia, the Russian Empire, allied with Serbia, declared war on Austria-Hungary; next, Austria-Hungary's major ally, the German Empire declared war on the Russian Empire and Serbia; then France, sided with the Russian Empire, declared war on the German Empire and Austria-Hungary; Britain declared war on the German Empire and Austria Hungary; and the last major power to join the war that year, Turkey, declared war on Britain, France, the Russian Empire and Serbia. Italy, an ally of the German empire and Austria-Hungary, declared its neutrality in 1914; it would enter the war on the Russian Empire, France, Britain and Serbia's side in 1916.