On June 28, 1914, Franz Ferdinand, Archduke of Austria and his wife Sophie are assassinated in Sarajevo by young Serb nationalist Gavrilo Princip, the casus belli of WWI. From the article:
"On 15 June 1910, Bogdan Žerajić attempted to kill the iron-fisted Governor of Bosnia and Herzegovina, General Marijan Varešanin. Žerajić was a 22-year-old Orthodox Serb from Nevesinje, Herzegovina, who was a student at the Faculty of Law at the University of Zagreb and made frequent trips to Belgrade.[12] (General Verešanin went on to crush the last Bosnian peasant uprising in the second half of 1910).[13] The five bullets Žerajić fired at Varešanin and the fatal bullet he put in his own brain made Žerajić an inspiration to future assassins, including Princip and Princip's accomplice Čabrinović. Princip said that Žerajić "was my first model. When I was seventeen I passed whole nights at his grave, reflecting on our wretched condition and thinking of him. It is there that I made up my mind sooner or later to perpetrate an outrage."[14]
In 1913, Emperor Franz Joseph commanded Archduke Franz Ferdinand to observe the military maneuvers in Bosnia scheduled for June 1914.[15] Following the maneuvers, Ferdinand and his wife planned to visit Sarajevo to open the state museum in its new premises there.[16] Duchess Sophie, according to their eldest son, Duke Maximilian, accompanied her husband out of fear for his safety.[17]
As Sophie, although of high aristocratic birth, was not from a dynastic family, her union with the Habsburg heir presumptive could only be a morganatic marriage. Emperor Franz Joseph had only consented to their marriage on the condition that their descendants would never ascend the throne. The 14th anniversary of their marriage fell on 28 June. As historian A. J. P. Taylor observes:
Photograph of the Archduke and his wife emerging from the Sarajevo Town Hall to board their car, a few minutes before the assassination
[Sophie] could never share [Franz Ferdinand's] rank ... could never share his splendours, could never even sit by his side on any public occasion. There was one loophole ... his wife could enjoy the recognition of his rank when he was acting in a military capacity. Hence, he decided, in 1914, to inspect the army in Bosnia. There, at its capital Sarajevo, the Archduke and his wife could ride in an open carriage side by side ... Thus, for love, did the Archduke go to his death.[18]
Franz Ferdinand was an advocate of increased federalism and widely believed to favor trialism, under which Austria-Hungary would be reorganized by combining the Slavic lands within the Austro-Hungarian empire into a third crown.[19] A Slavic kingdom could have been a bulwark against Serb irredentism, and Franz Ferdinand was therefore perceived as a threat by those same irredentists.[20] Princip later stated to the court that preventing Franz Ferdinand's planned reforms was one of his motivations.[21]
The day of the assassination, June 28 (June 15 in the Julian calendar), is the feast of St. Vitus. In Serbia, it is called Vidovdan and commemorates the 1389 Battle of Kosovo against the Ottomans, at which the Sultan was assassinated in his tent by a Serb."