Trifko Grabež society. For the next two years he spent most of his spare time with other nationalists who favoured a union between Bosnia and Herzegovina and Serbia. When it was announced that Archduke Franz Ferdinand, the heir to the throne of Austro-Hungarian Empire, was going to visit Bosnia and Herzegovina in June 1914, Colonel Dragutin Dimitrijević, the chief of the Intelligence Department in the Serbian Army and head of the Black Hand, sent seven men, Grabež, Nedeljko Čabrinović, Vaso Čubrilović, Cvjetko Popović, Danilo Ilić, Muhamed Mehmedbašić and Gavrilo Princip to Sarajevo to assassinate him. Each man was given either a revolver
Danilo Ilić Mehmedbašić, and Cvjetko Popović to assassinate Archduke Franz Ferdinand of Austria, which it that led directly to World War I. He and Gavrilo Princip were close friends. On Sunday, 28 June 1914, Franz Ferdinand and Sophie von Chotkow were assassinated by Gavrilo Princip. Princip and Nedeljko Čabrinović were captured and interrogated by the police. They held out, but Ilić, who was picked up on a routine check, eventually broke down under pressure and named his fellow conspirators. Muhamed Mehmedbašić managed to escape to Serbia but Veljko Čubrilović, Vaso Čubrilović, Cvjetko Popović and Miško Jovanović as well as Danilo Ilić were