Also the Yugoslav Wars of 1990s
I can say that /u/Denswend did an excellent summary. What I will add is just some human stories specific to Yugoslav wars.
To preface, Croatia is very popular summer tourist destination for Slovaks. The language is familiar (although not entirely understandable) but moreover the food, the culture and communist historical experience is something weirdly comforting. This all together with friendliness and laid back attitude of Balkan Slavs makes them very endearing to us. We jokingly refer to Adriatic sea as (Czecho)Slovak sea.
So no surprise that for instance over some years when I visited Croatia for boating trips I built friendship with local skipper. Couple of years into my experience one night where it was just two of us left in discussion of all the people on the boat safely anchored in marina I engaged him with the talk about his Yugoslav war experience. He served in those wars as very young conscripted soldier. He had the usual army jokes and experience that could have been told by my uncle - how they smuggled a truck full of beer for the soldiers under shady circumstances and so on.
Once, after we had maybe 5 or 8 beers more than would be advisable he opened about darker side of his experience. Two stories stood out.
One was when he was deployed in combat situation in the woods near the town where he was born. The fighting was fierce and the opposing forces got so close that enemy soldiers could hear each other. Now an intermezzo - Croatian and Serbian are very close languages, almost a dialect. The main difference is that for historical reason (Croatia being Catholic part of Austria while Serbia being Orthodox part of Hungary) they use different alphabets (Latin for Croatia and Azbuka for Serbia). Now this Croatian is shooting in the forest toward enemy positions and he hears enemy calling names of people and he recognizes nickname of somebody he went to school - one of his best friends who was with him in school soccer team. So he shouts back "hey nickname, is it you Johnny?". Enemy replied: "Yes, it is me. Is it you, Brad?" Luckily, they recognized each other and were moved enough to persuade their comrades - after an awkward moment - both platoons had some 1914 Christmas truce moment of their own. They just could not kill each other. Tragic if you ask me.
This was an awesome story. I will not lie, I could not verify if it was true, but it seemed true enough to me. The worst part of Yugoslav wars was that Croats and Serbs were not neatly arranged in corners. Most people in Croatia were Catholics and Croats. Most people in Serbia were Serbs and Orthodox. But there were enclaves all over both countries, many times even families. That is why this fucking war was so fucking terrible. I was not there, but it is stuff of nightmares.
Anyway, let's continue. After another beer or two (and after we both bonded over pissing into the sea in the marina) I asked the smart ass question as I educated myself on Yugoslav war. I asked this Croatian skipper: Hey man, were you part of Operation Storm by Ante Gotovina? At first, he started to talk a bit about how they prepared for it. And then he could not continue. I did not press further.
All I have to say is that Yugoslav wars were absolutely terrible and beyond something that I am comfortable judging from the standpoint of regular participants easily. It is still in living memory and as somebody who had family in Slovakia where during WW2 there was similar internal conflict I do understand.
All I can say is to promote healing and cooperation of all people - Croats and Serbs and other peoples alike. Which is yet another reason why I really hate this racial divisiveness that comes from USA.