Located in southwestern Yugoslavia, the provinces of Bosnia and Herzegovina were long ruled by their various neighbors. After nearly five centuries of Ottoman Turkish rule, they were placed under Austrian protection in 1878, and a year later their first separate stamps appeared. In 1908, Austria-Hungary formally annexed Bosnia-Herzegovina, arousing the fears of Serbian nationalists, who sought to add the area to the Kingdom of Serbia. In 1914, Austrian Archduke Ferdinand, heir to the aging Austrian emperor, was assassinated at the capital, Sarajevo, by agents of the Serbian secret police, setting off the series of events that culminated in World War I. After World War I, Bosnia and Herzegovina became part of the newly established Kingdom of Yugoslavia. During World War II, ancient ethnic antagonisms were renewed and reinforced as Croats, Serbs and Muslim Bosnian forces fought one another. In 1991 the Bosnia and Herzegovina parliament declared the states sovereign and in early 1992 declared independence from Yugoslavia. This was bitterly opposed by ethnic Serbs, and a three-way civil war broke out, with the loosely allied Croat and Muslim factions, backed by Croatia and later NATO, fighting the Bosnian Serbs, supported by Yugoslavia, which was by now reduced to the core Serbian state. This civil war was marked by atrocities and by the Serbs' ruthless policy of ethnic cleansing, the expulsion or execution of non-Serb minorities in the areas they controlled. In 1995 a peace agreement divided the country between the Croat-Muslims and the Serbs and created a collective government. Since then, a shaky peace has been maintained by a large international peace-keeping force.