Bosnia and Herzegovina the annexation proclamation on 6 October 1908. Despite international furor and objections to the Austro-Hungarian annexation, Russians and their client state, Serbia, were compelled to accept the Austrian-Hungarian annexation of Bosnia Herzegovina in March 1909. In 1910, Habsburg Emperor Franz Joseph proclaimed the first constitution in Bosnia, which led to relaxation of earlier laws, elections and formation of the Bosnian parliament, and growth of new political life. On 28 June 1914, a Yugoslav nationalist youth named Gavrilo Princip, a member of the secret Serbian-supported movement, Young Bosnia, assassinated the heir to the Austro-Hungarian throne, Archduke Franz Ferdinand, in Sarajevo—an event
Assassination of Archduke Franz Ferdinand 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. A Slavic kingdom could have been a bulwark against Serb irredentism, and Franz Ferdinand was therefore perceived as a threat by those same irredentists. Princip later stated to the court that preventing Franz Ferdinand's planned reforms was one of his motivations. 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