World War I
World War I saw the final dissolution of the Ottoman and the Habsburg Empires. A new south Slavic state called the Kingdom of Serbs, Croats and Slovenes was formed in 1918.
The new state was established as a constitutional monarchy with a parliamentary system, headed by King Alexander of the Serbian royal family, and included Serbia, Montenegro, and parts of the former Austrian Empire. Delegations from Macedonia, who sought autonomy or union with Bulgaria on ethnic grounds, were ignored. U.S. President Woodrow Wilson's support, however, did preserve Albania from dismemberment, which was desired by Italy, Greece and Serbia.
Serbs and Croats
The great internal conflict of the first Yugoslavia was over the degree of central control. Serbs were the largest national group in the country (39%) and the victors of the First World War. Many Serbs and their leaders considered the new Slavic state as "theirs." The Kingdom was administered as one unit with 33 provinces ruled from Belgrade.
The second largest national group, the Croats (24%) sought greater decentralization, and even autonomy. Serb hegemony also encountered resistance in Kosovo and Macedonia.
In 1929 King Alexander abolished the constitution and established a personal dictatorship.
Political violence was a fact of life in inter-war Yugoslavia. For example, A Serb member of parliament murdered the leader of the Croatian Peasant Party, Stjepan Radic, and killed or wounded several other Croat representatives on the floor of parliament in 1928. King Alexander was himself assassinated in 1934 while on a visit to France.
In August 1939, Croatian political leaders persuaded the central government to grant Croatia autonomy. Slovene and Muslim demands quickly followed, reducing Yugoslavia's capacity to operate as an effective state.