Adrift in an ocean of Christianity, most Albanians and a significant number of Bosnians are Muslims, left over from when the Ottoman Empire ran that corner of Europe. In this place of long memories and short tempers that would be enough to stir up trouble but it's too simple for a place like the Balkans. The Christians come in two flavours. Orthodox Serbs and Catholic Croats are not known for their Christian brotherly love towards one another. The Croats betting on the wrong side in the second world war didn't help things much either.
Religion is merely the most obvious dividing characteristic.
The only people the Muslim Albanians hate more than the Orthodox Serbs are each other. When someone said something bad about someone's mother in the fifteenth century, the story got handed down through the generations. Blood feuding is a national sport. Much like Tito's Yugoslavia, it's only been the grip of a dictator that has kept a lid on the violence. Thankfully, too many centuries of religious, ethnic, and tribal hatred is about to come to an end.