Durpari Army vs Raurindi Dervishes

Following the collapse of the Raurin Empire, the lesser kingdoms and principalities of the region broke away and became independent. The strongest of these was the kingdom of Durpari, a nation of merchants, traders, bankers and moneychangers. Previously considered little more than shopkeepers with airs above their station by many of the surrounding nations, they had unsuspected power thanks to the great wealth the king of the time had amassed in the royal treasury. They did not hesitate to use it to establish themselves as the pre-eminent power of the former empire, through a combination of military strength, mercenaries, and trade deals which handicapped any foreign nations which may have tried to oppose them.
Although the Durpari never attained the dominance of their former overlords, they remain a significant power to this day. They control the once-heartland of the former Raurin empire, with the scattered Raurindi desert tribes which are all that remain of the once-great nation. Religious differences have created significant contention between the two groups, however.
The Raurindi accept and worship a multiplicity of gods, believing that all must be venerated if any are to be considered valid. This is in stark contrast to the monotheistic Durpari, who revere the god Anu, god of merchants. Once a demigod, Anu managed to marshal enough power to make the ascent to lesser godhood, but not enough to challenge the prime pantheon for a position. As a result, he is jealous of anything which might be perceived to challenge his power or status, and orders his followers not to tolerate any other form of worship within the borders of their realm.
Repeated attempts by the Raurindi to crush the polytheistic practices of the Raurindi tribes have been beaten back by the Dervishes, holy warriors of the tribes, and an uneasy peace has settled over the region. This only lasts until a charismatic and aggressive priest of Anu stirs up religious fervour among the faithful once again, and conflict breaks out.
Whenever the simmering tensions escalate, the Anuban faithful start to destroy the shrines used by the Raurindi tribes. The Raurindi retaliate, then the Durpari army is called in to restore order; and, if the priest who caused the problems is sufficiently highly-ranked, to forcibly pacify the Raurindi. Dervish-warriors rise from amongst the tribesmen to defend their people and their gods, and are usually able to beat back the Durpari armed forces until cooler heads prevail, and peace is negotiated once more. This cycle has lasted for several centuries.