More important is new split after the war from 1992-1995 on Republic of Srpska where live most of the Serbs and Federation where live most of the Croats and Bosniacs, with tendencies of another split between Croats and Bosniacs.
During 1992-1995, countries around us, Serbia, Croatia and Montenegro committed a genocide on Bosnia and Herzegovina, in order to completely erase Bosniaks off Balkan. These tendencies, however, weren't born only 20 years ago, they existed since the Ottoman Empire left these parts. For centuries, Bosniaks were people of Bosnia (which was first mentioned in 10th century by Constantine VII Porphyrogennetos), no matter what their religion is. However, in 1878 Austria-Hungary came and started splitting people of Bosnia, on religious basis. So, Bosniaks became exclusively Muslims, Catholics became Croats, and Orthodox became Serbs. And actually, Bosnian Catholics and Orthodox Christians are not Serbs or Croats, because their roots are from Bosnia. But well... there's no coming back.
Those separations are dumb. Bosniaks are all people from Bosnia, or anyone who considers him as a Bosniak, no matter what their religion is. Even in Switzerland not all people are the same religion, but that doesn't change their national identity, for God's sake.
Back to genocide;
People will often refer to it as a civil war, but it was something way beyond that. SFRJ army broke into Bosnia and started killing innocent people, destroying religious objects and objects of cultural value. No human rights were respected. There is simply no words for horrors that occurred only ~20 years ago. It's the greatest disaster after the World War II.
The country is now split into two parts : Federation and Republic of Srpska (which is a result of a genocide), as acmilano said, however, if you ask me, those do not exist. Bosnia and Herzegovina is an independent, inseparable state. However, Serbs in both Serbia and Republic of Srpska are so shameless and arrogant that they claim Bosnia doesn't exist at all. They insult war victims, and desecrate everything that is holy. They really are mentally rotten people, they disgust me. Even now, sometimes, I get messages on different sites, eg. YouTube, where some retarded 11 year old Serbian monkey insults and threatens me, and claims that we Bosniaks do not exist as a nation, and that we are all Serbs. He also said something like, "you are Islamicized Serb, you better convert to Orthodox Christianity and claim Serbia as your homeland, you'll end up dead, with your throat cut in some river anyway."
Here you can see what I'm talking about. And that's not only one person - the whole nation acts like that. They're so narcissistic and self-obsessed, and the fact is, most of the things they claim as facts are based on lies. Two most important lies they base their tendencies on are:
1. Bosniaks do not exist.
Uh-huh, the Bosnia, along with Bosniaks were first mentioned back in 10th century, in Constantine VII Porphyrogennetos's "De Administrando Imperio" which was made between 949-955, as I said before.
2. Bosnian language does not exist.
Actually, the fact is, Serbian language was made of Bosnian. Vuk Karadžić, someone who they're really proud of, took Bosnian dictionary, re-wrote it, changed it a little, and there it is. Same thing happened with Croatian language, but I assure you, they will rather die than admit it.
Oh, and that another split, between Croats and Bosniaks, is not going to happen.
If someone considers him as a Croat, well, the Croatia is west from here, so buyrum. Same for Serbs - Serbia is on the east. Bosnia is for Bosniaks, no matter what religion they are.
I accept EVERY religion, but there's no room for a state in a state in another state. We have enough problems with this Republic of Srpska, and that has to be torn down as soon as possible.
The state is now critical, corrupt politicians, dumb system, and there's always a pressure from all sides. Basically, Bosniaks are now trapped in between. Bosnia is now amongst 20 poorest countries on the world. About 50% of people are unemployed. Still, you may see lots of BMW X6s, few Audi R8, big ass houses. Thing is, all wealth is concentrated and unevenly distributed.
"When Yugoslavia broke up did many people leave their region to go to one of the new countries that reflected their ethnic background or did people just mostly stay where they were?"
They mostly stayed where they were. Yugoslavia was a state, which intended to unify people on Balkan. In 1990s, countries started separating from Y , and the borderlands stayed the same way they were before those countries joined Yugoslavia. Serbia attacked those countries which seceded themselves.Only Macedonia had luck to do it peacefully. Serbs attacked Slovenians, but they somehow, cut them off quickly. Then came Croatia, which also sustained losses, but Bosnia paid the highest price.
Well, it was a good thing, but it was based on evil intentions. It was some shape of the 'Great Serbia' and 'Great Croatia' thing, it's something that was born long ago, and Yugoslavia was, indirectly, a way to realize it.
You know, Yugoslavia was good thing for ones, and bad for others. The system was way better and more organized than it is now in countries it consisted of. People had jobs, worked in large firms which gave them flats. But, at the same time, many things were unorganized. Example, Bosniaks were completely neglected as a nation, along with Bosnian language, too. You could determine yourself only as a Serb, a Croat, or Others. Much later, Bosniaks reverted their national identity and language.
Didn't work out well. You cannot connect sky and land, that's it.