What triggered the violence in the Balkan Peninsula in the 1990s and how was it resolved?
The primary trigger to the violence in the Balkans was the death of Marshall Tito in 1980. It was only through the strength of his dictatorial regime that the individual states were stabilized. After approximately 10 years, the diverse populations were no longer willing to resist the pull of independence.
The violence was a result of not just the racial divisions in Yugoslavia but the religious ones as well. These led to the political differences. For example, the two largest parts of the Republic were Croatia and Serbia. Although both are Christian, there are significant differences. Croatia is more Western, therefore closer in proximity to Europe and that includes Rome and Germany. Rome is important because of Roman Catholicism and Germany has obvious historical references to World War II. Serbia is closer to the former USSR, which had traditional problems with Germany and in their religion they were coser to the Eastern Orthodox Church.
Slovenia was actually farther to the west than Croatia, so they were physically more removed from the conflict. The most significant issue with Bosnia and Herzegovina was that they were between their much larger relatives, Croatia and Serbia. Even more significant is that they were overwhelmingly Muslim. So what you have in an area that is not that large, are historically diverse populations of people in their religious, racial and ultimately their politics.
There are Muslims and two branches of Christianity and all three have had their differences for over a thousand years. We should not try to disparage one area of a population for being excessively violent. But it goes without saying that all the peoples in the Balkans are capable of extreme violence and bravery. Don't forget that both Germany and the USSR had tried to conquer the Balkans in World War II and neither was successful.
The only way that is was resolved was that each part of the republic was given autonomy. However that was not a simple matter. That was why the violence occurred very early, because the Bosnians were no match for the Croats or the Serbs. The United Nations as a whole as well as great individual effort by the USA and our European allies that had very much to lose with continued warfare, was the only way the conflict slowed down to the point that peace talks could begin under former President Clinton in Ohio.