The end-game of Communism in some of the places that had been part of the Soviet Union and Yugoslavia was much more violent than in other places such as Czechoslovakia, home of the Velvet Revolution.
The violence took place between different nations that had been thrown together in the same state.
I'm not a lawyer, let alone an international lawyer, but I'm using the terms "state" and "nation" according to what I understand to be their technical legal meanings, which are different than the way we use those words in American political conversation.
"State" means an independent country. But since, of course, we apply that word to political subdivisions of our country, we tend to call an independent country a "nation". But the international meaning of "nation" is a people with a common culture, which may or may not have a state of their own.
So, for example, there is a Japanese nation and a Japanese state. However, there is a Kurdish nation, but no Kurdish state. And to illustrate one more variation on the theme, Belgium, for example, is a state with two nations (Flemings and Walloons).
The USSR and Yugoslavia consisted of multiple nations crammed into a single state. The USSR created that situation by conquest, while Yugoslavia was somewhat of an artificial creation, as part of the Versailles peace settlement after World War I.
There is a story about the creation of Yugoslavia that gets repeated so often, I assume it must be apocryphal. But, whether it happened or not, it makes a good story, especially for a Republican to tell. Supposedly, President Woodrow Wilson, representing the U.S. at the Versailles peace conference in 1919, micromanaged the creation of Yugoslavia to such a degree that, at one point, he was down on his knees, drawing boundaries on a map that was placed on the floor. In a PBS interview in 1999, journalist Harold Evans describes:
... when Wilson went to Versailles to make the world safe for democracy and was on his knees drawing a map of Yugoslavia on the principle of self-determination ...
Serbians, Croats, Slovenes, Bosnians, Montenegrins and Macedonians were combined into Yugoslavia, the land of the South Slavs. The boundaries needed to be redrawn because those areas had been part of the Austro-Hungarian empire, which was broken up when it ended up on the losing side in World War I.
The notion that Yugoslavia was totally dreamed up in Wilson's idealistic head is at least an exaggeration. Srdja Trifkovic, writing under the auspices of the Hoover Institution at Stanford, describes unification efforts by some of the people in those nations, that predated Wilson.
But regardless of who gets the credit or blame for its creation, the fact remains that multiple nations with disparate cultures were combined in one state. Among other differences, Yugoslavia threw together Catholic and Orthodox Christians, as well as Muslims.
Next: What held the Soviet Union and Yugoslavia together, temporarily?