The funny thing about that is that Islam contains a rather strong condemnation of fighting other Muslims, particularly for tribal reasons. Muslims are supposed to go kill the heathens, not each other.
But the Muslims have never really followed the rules in the Koran about treating every other Muslim as a brother. Even at the peak of Islamic culture, Muslims of Arabian decent considered themselves better then Muslims from other regions. And through out Islamic history there have been sects of Muslims fighting against each other, and various tribal groups that follow Islam have been in fighting since well before the religion existed.
Jay