Centuries of foreign domination by empires, kings and landlord gentry of feudalism and then capitalism had a tremendous effect on these people, since all Empires wanted to hold this strategic and valuable piece of real estate in their hands.
Yugoslavia is made up of the same ethnic roots, language and customs, but over hundreds of years under different occupations they were forcibly converted into different religious groupings split into small “nationalities.”
In the 13th century Ottoman Turks took Serbia at the Battle of Kosovo and by the late 15th century the Turks also ruled Bosnia-Herzegovina. For 400 years of Turkish conquest generations of these Slavs had to convert to Islam and thus a split took place between Muslims and Orthodox Christians.
In 1526 other Slavs such as Croatians and Slovenes came under the Austrian king's control and the conversion to Catholicism started; thus another split in South Slavs took place. Tensions started between Serbs and Croatians when Austrians forcibly relocated hundreds of thousands of Serbs to the Croatian-Bosnian borders, today known as Krajina.
At the 1878 Congress of Berlin, after Russia's defeat of the Turks, Serbs were able to gain their independence. But the big power-brokers such as England split Serbia by force of arms and gave back to Turkey the Kosovo and Macedonian territories, while the great powers gave to Austro-Hungarians the Bosnia-Herzegovina territories without giving any regard to the wishes of the people to be united as South Slavs.
After the defeat of the Austro-Hungarian Empire after the First World War, the big powers this time included England, France, USA, there took place a unifying movement under King Alexander and he renamed the country Yugoslavia, which means Country of South Slavs.
Remember that this was a capitalist country and did the bidding of the Big Powers in its domestic and foreign policies.
The Croatians, under the influence still of Austro-Germans, started a separatist movement and in 1929 formed a fascist separatist movement called the Ustashe. They were supported by Italian Fascists and the upcoming German Nazis.
In 1941 Germany invaded Yugoslavia and partitioned it, rewarding the Croatian Ustashe regime and armed the fascist state of Croatia, an ally of Germany. Hundreds of thousands of Serbs, Jews and Gypsies were massacred by the Croatian fascists, and many times with the Turkish-influenced Bosnian Muslims, who actually are Slavs and speak the Slavic languages. The Croatian Ustashe forced thousands upon thousands of Orthodox Serbians to be baptized as Catholics, on the pain of death. Serbs of course went to the defense of their brothers and sisters and thus the Yugoslav partisans not only fought the German fascists but they had to fight the Croatian Ustashe fascists also. Over one million Yugoslavs died in order to liberate Yugoslavia from the German fascists and the local Croatian Ustashe butchers.
Marshal Tito, himself a Croatian, made the country into the Yugoslav Federation with 6 autonomous republics. Kosovo in this context was a pawn even after 1945 in the hands of Western Imperialism in order to undermine the anti-fascist unity that was forged against fascism.
Communists should know what Tito did and how things could have been different in the Socialist world if Tito's policies did not lead to subversion and open collusion with the West. His policies regarding ethnic problems were not altogether based on Marxism-Leninism. Western powers were always in this region before, as they are now, stirring ethnic conflicts, religious and political isms amongst the population in order to serve their own interests.
Imperialism, led by the USA is trying to revamp what took thousand years to be built up, namely the unity of the South Slavs that inhabit Yugoslavia and originally came from the Carpathian Mountains.
Time to resurrect the cry of Ibarruri: