The idea of a unified South Slavic state (typically expected to be spearheaded by independent Serbia) became a popular political ideology in the region at this time, including in Bosnia and Herzegovina. The Austro-Hungarian government's decision to formally annex Bosnia-Herzegovina in 1908 (the Bosnian Crisis) added to a sense of urgency among these nationalists. The political tensions caused by all this culminated on 28 June 1914, when a Young Bosnia revolutionary named Gavrilo Princip assassinated the heir to the Austro-Hungarian throne, Archduke Franz Ferdinand, in Sarajevo. The event set off a chain of events that led to the outbreak of World War I. Although 10% of the Bosniak population died serving in the armies or being killed by the various warring states, Bosnia and Herzegovina itself managed to escape the conflict relatively unscathed.