Bulgaria during World War I 28 June 1914, Gavrilo Princip, a Bosnian-Serb student and member of Young Bosnia, assassinated the heir to the Austro-Hungarian throne, the Archduke Franz Ferdinand of Austria in Sarajevo, Bosnia. This began a period of diplomatic manoeuvring between Austria-Hungary, Germany, Russia, France and Britain called the July Crisis. Wanting to end Serbian interference in Bosnia conclusively, Austria-Hungary delivered the July Ultimatum to Serbia, a series of ten demands that were intentionally meant to be unacceptable in order to precipitate a war with Serbia. When Serbia acceded to only eight of the ten demands levied against it in the ultimatum, Austria-Hungary declared
Robert, Archduke of Austria-Este assassinated relative Archduke Franz Ferdinand of Austria, (1863–1914), who had inherited in 1875 the Austria-Este designation and what had been salvaged of the Este fortune when the duchy was annexed to Italy in 1860. Archduke Robert descended through his Habsburg father from Ercole III d'Este, Duke of Modena, and his mother Zita was a descendant of Maria Beatrice d'Este, heiress of Modena and her husband, Archduke Ferdinand of Austria. Thus the lineage of the last Este dukes, in female descent, remained joined to the Austria-Este legacy. Archduke Robert eventually adopted use for himself and his descendants in male line the