This paper studies why and how the Turks and their successors, the Türgish, ruled the settled societies of Turkestan. It is based upon research in original Chinese and Arabic records. The most noteworthy sources are contemporary Chinese documents from Turfan that were excavated in this century and only recently published. These provide us with some heretofore unknown information about the tribes and their contacts with sedentary societies.
Although the Turks and Türgish were pastoral nomads, they had a keen interest in controlling the agricultural societies of Turkestan. Nomadic rulers used the oases to increase their wealth and power by levying local products, Silk Road trade profits, and soldiers. The Türgish conscripted oasis fighting forces more extensively than the Turks, probably because of their diminished territory and power in comparison to their predecessors.
    Nomadic rule of the oases usually was indirect. The only exceptions were the states of Shâsh, Farghânah, and Tukhâristân, which appear to have had Turkish kings. Unfortunately the Chinese and Arabic sources provide little evidence about how the Turks ruled over these settled areas. For indirect rule, we have more information, especially from the oasis that was closest to China, Turfan. When nomads governed indirectly, they allowed indigenous elites to keep their positions. Although nomadic overlords did not take over administration of these oases or garrison troops in them, they had a number of means to encourage compliance with their authority. To monitor the oasis states, Turkish rulers stationed a few officials there and also intermittently sent envoys. Undoubtedly the most important function of these Turkish functionaries was to see that adequate tribute was sent to their chiefs. Turkish overlords also implemented several co-optative and coercive strategies to keep oasis elites in line. The most important co-optative practice was the forging of marriage relations between nomadic and sedentary rulers. Coercive methods, used to enforce nomadic rule, were military attack and the imposition of Turkish customs among the sedentary peoples.
    Although we have no contemporary records of nomadic expenditures on oasis administration, we can assume costs were quite low because few personnel were needed. The tribute received in return must have resulted in high profits. We can suppose that this was an important income source for the Turks and Türgish to supplement their pastoral subsistence economy. The added wealth undoubtedly helped chiefs to attract more adherents and to increase their political power. Therefore it is not surprising that the tribes of Turkestan went into decline after the Chinese and then the Arabs gained control of the oases in the seventh and eighth centuries.