are they radical muslims or something?!
Hard to tell without knowing more. I can't identify the uniforms. Perhaps someone else can.
The vid appears to have been uploaded in 2008, but may, in fact , be older. In any case, it's related to the rancorous splitting of the country of Yugoslavia after the demise of Tito. The soldiers could be Bosnians (Muslims) or they could be Croatians (Catholics). These groups have a profound hostility to one another going back decades. (Sadly, the Croations are racially identical to the Serbs, but they're Roman Catholic as opposed to Orthodox. Alas, it makes no difference.) In any event, it's a combination of religion, politics, and nationalism.
Oh, and evil.