As mentioned before, president Tito was a very strong communist leader. After his death Yugoslavia quickly went down. The new leader, Slobodan Milosevic turned to nationalism and religious hatred. He made a very detailed plan. The first step was to light the old flame of the tension between Serbs and Muslims. The orthodox Catholic Serbs claimed the Albanian Muslims were mistreating them. "Serbian-backed political unrest in Kosovo eventually led to its loss of independence and domination by Milosevic". After both countries gained their independence, a civil war started. It was Yugoslavia(what was left of it) vs. Croatia and Slovenia. After a failed attempt to get Slovenia back, Milosevic lost interest. He turned his attention to Croatia where 12% of the population was made up of Orthodox Serbs.
During World War II, Croatia was a pro-Nazi state. The new Croatian government was reviving fascism, basically a dictatorship. They even started using the old flag and enabling laws aimed at Orthodox Serbs. Aided by Serbian guerrilas, Milosevic's forces invaded to 'protect' the Serbian minorities. The first attack was in Vukovar, they bombarded the unarmed Croats for 86 days until the city was rubble. After this Serbs began the mass murder, killing hundreds of Croat men, burying them in mass graves.
Internationally, the response was very minimal. President George Bush of the United States chose not to interact with military, however recognized Slovenia and Croatia's independence. A US cease-fire agreement was brokered between the Serbs and Croats fighting in Croatia. In 1992, the US decided to recognize Bosnia's independence too. It was recognized as a mostly Muslim country where the Serb minority made up on 32%.