Following World War 1, the first unified Yugoslavia was born, the kingdom of Serbs, Croats and Slovenes. Very quickly, the first separatist tensions appeared in Kosovo, and particularly in Croatia. This institutional entity did not survive World War 2, which was to plunge the Yugoslavian people into the darkest period of their history. In 1945, Tito created the Socialist Federal Republic of Yugoslavia. This new entity was a federation of peoples and republics placed under the authority of a sole party. At the end of the 1960s, the model that Tito had implemented was contested in Serbia, Croatia and Kosovo. When he died in 1980, socialist Yugoslavia was out of breath, undermined by divisions, incoherence and the resurgence of national tensions.