Serbian Campaign of World War I Serbia, Montenegro, and Greece. When Bulgaria attacked both Serbia and Greece on 16 June 1913, it lost most of its Macedonian region to those countries, and additionally the Southern Dobruja region to Romania and Adrianople (the present-day city of Edirne) to Turkey in the 33-day Second Balkan War, which further destabilized the region. On 28 June 1914, Gavrilo Princip, a Bosnian Serb student and member of a multi-ethnic organisation of national revolutionaries called Young Bosnia, assassinated Archduke Franz Ferdinand of Austria, the heir to the Austro-Hungarian throne, in Sarajevo, Bosnia. The political objective of the assassination was the independence of
Muhamed Mehmedbašić the way to Sarajevo, gendarmes searched the train; fearing they were on to him, he threw the knife out the window. Potiorek was planned to be assassinated at the end of March 1914, when the new mufti Čaušević was to be enthroned in Sarajevo. However, upon hearing that Archduke Franz Ferdinand of Austria would come to Sarajevo on Vidovdan, the Black Hand changed their minds. The Archduke's scheduled visit on Vidovdan (28 June), a Serbian national holiday, was perceived as an insult. Ilić summoned Mehmedbašić and informed him on 26 March that the plan now was to murder Archduke Franz