Yugoslavia means a South Slav state. The Yugoslav idea is a creation of the nineteenth century and the work of Croat thinkers. The most influential ideologist was Bishop Josip Strossmayer of Djakovo (1815-1905).His final goal was to unify all south Slav national units emerged after the breakup of Austria-Hungary with other south Slav states on equal terms, that is to found a federal south Slav state. In twentieth century, the Yugoslav idea was inherited to the Yugoslav Committee which represented the South Slavs within Habsburg Empire during the First World War and sought after a unified state with Serbia in postwar period. However, for long tome, Serbian Government had not show eagerness for the Yugoslav idea. Because their national program was to establish the Great Serbia, unifying in one country the scattered Serb settlements of the Balkans, not to create a joint south Slav state, with the Slovenians and the Croats as their partner. Nevertheless the south Slav unified state was realized in the long run. The continuing advance of Italian forces prompted a majority of the Zagreb National Council, the governing body of the ad hoc state of the former Austria-Hungarian south Slavs, to accept the Serbian regent's invitation to meet with him in Belgrade. Their representatives asked the regent Aleksandar to the unification and he proclaimed the Kingdom of Serbs, Croats, and Slovenes on December 1 in 1918. However, the representatives of National Council did not negotiate a unification treaty with Serbian government at all. They took for granted that the autonomy of the local government in the former Austria-Hungarian countries was guaranteed. But the Serbian leaders did not think that they made such a promise. The former Austria-Hungarian south Slavs soon realized that they had an illusion about the state, for it was quickly administered by old Serbia's army and bureaucracy according to old Serbia's constitutional and political models. That exacerbated the tension and differences among ethnic and social consti