Unlike a history of the city of Mosul, a history of the settled communities of the Marwānid Jazira cannot be written; and of all the problems, perhaps the most elusive concerns the (usually) slow processes of conversion, acculturation and assimilation, by which an Arabian language of monotheist reform was transformed into a rhetoric of territorial rule. Now one conventionally explains problems such as these with reference to the character of our source material, which says so little about the Late Antique world in which early Muslims settled. This is of course true; but it must also be said that the material generally reflects the prevailing character of early Muslim belief, when Muḥammad's (apparent) marriage of ethnicity and creed had not yet been been dissolved. The tradition held that Jews and Christians had no place in the jazīrat al- 'arab (the Arabian Peninsula), but there were no such restrictions in the Jazira: as long as they paid the jizya, Jaziran Christians simply did not matter. Accounts of the conversion of a deracinated tribesman such as Ṣuhayb b. Sinān – the most famous of all early Jaziran/Byzantine Christians – predictably say more about the Shu'ūbiyya controversies of the second and third Islamic centuries than they do about the Jazira itself.

By contrast, the experience of immigrant tribesmen did leave an authentic mark on our sources, and one that can actually tell us something about nonurban élites.