I have a friend from Bosnia...He was in the war. The first time I asked him about the war he stiffened up and said it was a long story and he doesn't want to talk about it. The most I got out of him is that he is muslim, but he said he fought for both sides and after that he says he doesn't want to talk anymore...My question is how or why would he fight for both sides?
There were three sides involved, Bosniaks, Croatians and Serbs. While first two more often cooperated than not, there were times and places where Croats and Bosniaks fought each other. Often in local circumstances any two sides could cooperate, or at least have a functioning ceasefire, in order to concentrate against a locally dominant third. At the start of Bosnian war, that sort of cooperation was very pronounced among Bosniaks and Croats in Hercegovina. So, it would be quite possible for him to start the war as a Bosniak with Croatian troops. However, soon it was exactly Hercegovina where the fiercest fights between Croats and Bosniaks took place.
Another possibility was for him to be involved in the war in Slovenia. In that short conflict Yugoslav army was still not almost exclusively Serbian, and in fact many recruits from Bosnia were involved. Therefore he could have fought first for Yugoslav (that would later be popularly equated with Serbian) side, and later on Bosniak side.
Serb army started off as Yugoslavian National Army. It was a mandatory service from age 18 and also reservists from Bosnia were called in for service when the war broke out in Croatia. So you have had alot of Muslims and Croats fighting against Croatian army first, then Bosnian guvrement troops.