Creation of Yugoslavia

The creation of Yugoslavia was a series of events that resulted in the creation of the Kingdom of Serbs, Croats and Slovenes (later renamed Yugoslavia) as a political union of the South Slavs in 1918. Those events took place in the context of dissolution of Austria-Hungary at the end of the First World War on the basis of ideas of Yugoslavism.

The South Slavs living in the Habsburg monarchy were first represented by the Yugoslav Committee, an ad hoc group established to prevent fulfilment of territorial promises by the Allies to the Italy under the Treaty of London. The Yugoslav Committee was convinced that the threat can only be averted by political alignment with the Serbia that had announced, in the Niš Declaration, unification of the South Slavs as its objective. The Yugoslav Committee and the Serbia formalised cooperation by the Corfu Declaration on the future political union. The second group representing the South Slavs living in Austria-Hungary was the National Council of Slovenes, Croats and Serbs. In October 1918, the National Council declared independence of the State of Slovenes, Croats and Serbs encompassing South Slavic parts of disintegrating Austria-Hungary and negotiated the short-lived Geneva Declaration on the degree of centralisation of the future state. The agreement determining a confederal system of government was quickly renounced by Serbia. The State of Slovenes, Croats and Serbs came under combined pressure from the loss of territory to Italian advance across Istria and in Dalmatia and the threatened establishment of Greater Serbia amid violence by the Green Cadres and social unrest as well as rumours about a coup conspiracy.

In response, the National Council asked the Royal Serbian Army to help restore order and the council decided to seek quick unification. The council appointed a delegation tasked with traveling to Belgrade and asking the Serbia's Prince Regent Alexander to complete the unification with Serbia—itself enlarged by annexation of Vojvodina and the Kingdom of Montenegro. The delegation was given instructions to demand a federal system of government be established in the new state. The delegation ignored the instructions and asked for unification with few conditions. In response, the Regent proclaimed the Kingdom of Serbs, Croats and Slovenes on 1 December 1918.

Yugoslavia received a wider diplomatic recognition in June 1919 during the Paris Peace Conference which determined a portion of its borders. Further segments of national borders were determined by the 1920 Carinthian plebiscite and the Treaty of Rapallo after the Paris Peace Conference. In immediate aftermath of the proclamation of unification, the government and the Temporary National Representation were appointed to enact electoral law for the 1920 Constitutional Assembly election. The newly elected assembly adopted the Vidovdan Constitution in 1921.