[14] Following the assassination of Archduke Franz Ferdinand of Austria by the Bosnian Serb Gavrilo Princip and the outbreak of World War I, Serbia was invaded and occupied by a combined Bulgarian, Austrian and German force on 6 October 1915.

[15] The Dalmatian Croat politician Ante Trumbić became a prominent South Slavic leader during the war and led the Yugoslav Committee that lobbied the Allies to support the creation of an independent Yugoslavia.

[16] Trumbić faced initial hostility from Serbian Prime Minister Nikola Pašić, who preferred an enlarged Serbia over a unified Yugoslav state.

However, both Pašić and Trumbić agreed to a compromise, which was delivered at the Corfu Declaration on 20 July 1917 that advocated the creation of a united state of Serbs, Croats, and Slovenes to be led by the Serbian House of Karađorđević.

[18] The negotiations would end, with the delegation of the National Council of the State of Slovenes, Croats and Serbs led by Ante Pavelić reading the address in front of regent Alexander, who represented his father, King Peter I of Serbia, by which acceptance the kingdom was established.

[citation needed] The newly established Kingdom of Serbs, Croats and Slovenes participated in the Paris Peace Conference with Trumbić as the country's representative.

Nearly 40% of the rural population was surplus (i.e., excess people not needed to maintain current production levels), and despite a warm climate, Yugoslavia was also relatively dry.

[23] Manufacturing was limited to Belgrade and the other major population centers, and consisted mainly of small, comparatively primitive facilities that produced strictly for the domestic market.

The commercial potential of Yugoslavia's Adriatic ports went to waste because the nation lacked the capital or technical knowledge to operate a shipping industry.

[24] On the other hand, the mining industry was well developed due to the nation's abundance of mineral resources, but since it was primarily owned and operated by foreigners, most production was exported.

The Great Depression caused the market for them to collapse as global demand contracted heavily and the situation for export-oriented farmers further deteriorated when nations everywhere started to erect trade barriers.

Italy was a major trading partner of Yugoslavia in the initial years after World War I, but ties fell off after Benito Mussolini came to power in 1922.

Because the Democratic Party led by Ljubomir Davidović pushed a highly centralized agenda a number of Croatian delegates moved into opposition.

The results left Nikola Pašić in a very strong position as the Democrats had no choice but to ally with the Radicals if they wanted to get their concept of a centralized Yugoslavia through.

The Croatian Republican Peasant Party refused to swear allegiance to the King on the grounds that this presumed that Yugoslavia would be a monarchy, something that it contended only the Constituent Assembly could decide.

In the early 1920s, the Yugoslav government of prime minister Nikola Pašić used police pressure over voters and ethnic minorities, confiscation of opposition pamphlets[29] and other measure to rig elections.

The provision for a secret ballot was dropped, and pressure on public employees to vote for the governing party was to be a feature of all elections held under Alexander's constitution.

As a response, Albert Einstein and Heinrich Mann sent an appeal to the International League of Human Rights in Paris condemning the murder, accusing the Yugoslav government.

[39][40][41] Croat opposition to the new régime was strong and, in late 1932, the Croatian Peasant Party issued the Zagreb Manifesto which sought an end to Serb hegemony and dictatorship.

On 9 October 1934, the king was assassinated in Marseille, France, by Bulgarian Veličko Kerin (also known by his revolutionary pseudonym Vlado Chernozemski), an activist of IMRO, in a conspiracy with Yugoslav exiles and radical members of banned political parties in cooperation with the Croatian extreme nationalist Ustaše organisation.

His solution to solving the economic problems left over from the Great Depression was to make trade deals and get closer to Fascist Italy and Nazi Germany.

The expansion of Nazi Germany in 1938 gave new momentum to efforts to solve these problems and, in 1939, Prince Paul appointed Dragiša Cvetković as prime minister, with the goal of reaching an agreement with the Croatian opposition.

Following the July 1943 fall of the Fascist regime in Italy, Tomislav II abdicated from his Croatian throne and Pavelić assumed direct control over the NDH, annexing the Italian Governorate of Dalmatia in the process.

From 13 May 1941, the largely Serb guerilla force, Chetniks ("Yugoslav Army of the Fatherland", Jugoslovenska vojska u otadžbini, or JVUO) resisted the Axis occupation of Yugoslavia and supported Peter II.

These hostile relations were demonstrated on 1 November 1918, when Italian forces sunk the recently captured Austro-Hungarian battleship SMS Viribus Unitis being used by the State of Slovenes, Croats and Serbs.

By the mid-1930s, France, internally divided, was increasingly unable to play an important role in Eastern Europe and support its allies, many of whom had suffered badly from the economic crisis of that period.

In October 1940 it attacked Greece, by when France had already been eliminated from the scene, leaving Britain as Yugoslavia's only potential ally – given that Belgrade had not recognized the Soviet Union.

Two days later, Prince Paul was deposed in a coup d'état and his nephew Peter II was proclaimed of age, but the new government, headed by General Simović, assured Germany it would adhere to the Pact.

Beside "Serbo-Croato-Slovene" (which includes Macedonian, then recognized as a southern dialect of Serbian), the most widely spoken languages by number of speakers were Albanian, Italian, Hungarian, German, Slovak and Rusyn.

[47] Aside from Vlachs, the Yugoslav government awarded no special treatment to non-Slavic ethnic minorities in terms of respect for their language, culture, or political autonomy.