"Islam has struck deeper roots on the coast, and has tended to be at its most self- conscious among trading communities. There has often been tension, and sometimes devastating warfare, between the coast and the interior. Although it is attractive to think of Islam as a causative factor in this conflict, it would probably be more correct to think of it as deriving from primary economic and political differences, with a rather more self- conscious Islam providing from time to time a convenient rallying banner for the coastal states."