Causes of World War I corrective." British Diplomat Arthur Nicolson wrote in May 1914, “Since I have been at the Foreign Office I have not seen such calm waters.” On 28 June 1914, Archduke Franz Ferdinand of Austria, heir presumptive to the Austro-Hungarian throne, and his wife, Sophie, Duchess of Hohenberg, were shot dead, by two gun shots in Sarajevo by Gavrilo Princip, one of a group of six assassins (five Serbs and one Bosniak) coordinated by Danilo Ilić, a Bosnian Serb and a member of the Black Hand secret society. The assassination is significant because it was perceived by Austria-Hungary as an existential challenge
Serbs of Croatia of the World War I, all organizations that the government considered favored unification of South Slavs or Serbia, which was on the side of the Allied Powers, were banned. Josip Frank's associates took advantage of some provocations and the anger of the people after the assassination of Archduke Franz Ferdinand by Serb Gavrilo Princip and organized anti-Serbian demonstrations. After a stone was thrown on a parade in which the image of Franz Ferdinand was carried true Zagreb, many cafés and gathering places of pro-Yugoslav politicians as well as Serb-owned shops were demolished. Croat-Serb Coalition MP's were also attacked. On the