volunteers led by Franjo Malgaj attempted to take control of southern Carinthia. Fighting in Carinthia lasted between December 1918 and June 1919, when the Slovene volunteers and the regular Serbian Army managed to occupy the city of Klagenfurt. In compliance with the Treaty of Saint-Germain, the Yugoslav forces had to withdraw from Klagenfurt, while a referendum was to be held in other areas of southern Carinthia. In October 1920, the majority of the population of southern Carinthia voted to remain in Austria, and only a small portion of the province (around Dravograd and Guštanj) was awarded to the Kingdom of Serbs, Croats and Slovenes. With the Treaty of Trianon, on the other hand, Kingdom of Yugoslavia was awarded the Slovene-inhabited Prekmurje region, which had belonged to Hungary since the 10th century. Border with Italy In exchange for joining the Allied Powers in the First World War, the Kingdom of Italy, under the secret Treaty of London (1915) and later Treaty of Rapallo (1920), was granted rule over much of the Slovene territories. These included a quarter of the Slovene ethnic territory, including areas that were exclusively ethnic Slovene. The population of the affected areas was approximately 327,000 of the total population of 1.3 million Slovenes. Kingdom of Yugoslavia In 1921, against the vote of the great majority (70%) of Slovene MPs, a centralist constitution was passed in the Kingdom of Serbs, Croats and Slovenes. Despite it, Slovenes managed to maintain a high level of cultural autonomy, and both economy and the arts prospered. Slovene politicians participated in almost all Yugoslav governments, and the Slovene conservative leader Anton Korošec briefly served as the only non-Serbian Prime Minister of Yugoslavia in the period between the two world wars. In 1929, the Kingdom of Serbs, Croats and Slovenes was renamed to Kingdom of Yugoslavia. The constitution was abolished, civil liberties suspended, while the centralist pressure intensified. Slovenia was renamed to Drava Banovina. During the whole interwar period, Slovene voters strongly supported the conservative Slovene People's Party, which unsuccessfully fought for the autonomy of Slovenia within a federalized Yugoslavia. In 1935, however, the Slovene People's Party joined the pro-regime Yugoslav Radical Community, opening the space for the development of a left wing autonomist movement. In the 1930s, the economic crisis created a fertile ground for the rising of both leftist and rightist radicalisms. In 1937, the Communist Party of Slovenia was founded as an