Year: 1918
As an outcome of World War I, the Kingdom of the Serbs, Croats, and Slovenes is formed. Croatia, Slovenia, and Bosnia and Herzegovina had been part of the fallen Austro-Hungarian empire; Serbia and Montenegro existed as an independent state (Macedonia was then part of Serbia).
Dec 1, The Kingdom of Serbs, Croats and Slovenes [later in 1929 to be called Yugoslavia] was proclaimed by Alexander Karadjordjevic, the son of King Peter of Serbia. It included the previously independent kingdoms of Serbia and Macedonia, the Hungarian-controlled regions of Croatia and Slovenia, the Austrian province of Dalmatia, Carniola and parts of Styria, Carinthia and Istria. King Alexander I renamed the Balkan state called the Kingdom of Serbs, Croats, and Slovenes to Yugoslavia in 1929