Just a history view … The six constituent republics that made up in the history the Republic of Yugoslavia were the Bosnia and Herzegovina, Croatia, Macedonia, Montenegro, Serbia, and Slovenia. Serbia contained two Socialist Autonomous Provinces, Vojvodina and Kosovo, which after 1974 were largely equal to the other members of the federation. After an economic and political crisis in the 1980s and the rise of nationalism, Yugoslavia broke up along its republics’ borders, at first into five countries, leading to the Yugoslav Wars. From 1993 to 2017, the International Criminal Tribunal for the former Yugoslavia tried political and military leaders from the former Yugoslavia for war crimes, genocide and other crimes.
In 2003 the Federal Republic of Yugoslavia was renamed to State Union of Serbia and Montenegro. The union peacefully broke up when Serbia and Montenegro became independent states in 2006, while Kosovo proclaimed its independence from Serbia in 2008. ~wiki