Orkhan solved this problem by establishing a system of rewards for military service, and then by restricting military service to Moslems. He divided the land he had conquered among his faithful warriors, and let it be known that in future conquests a large portion of the territory won, outside of the cities, would be bestowed upon soldiers who took part in his campaigns. These lands were to be held as military fiefs. The only obligation was that of military service, which could be performed either by actually putting into the field a number of men in proportion to the land held or by paying a sum sufficient to replace the quota by hired troops. So far this was but an adaptation of the European feudal system. But it was superior to the European system in that the holdings were small and that there was through two centuries an ever-present opportunity of winning new holdings. Except in Albania and Bosnia, where the old nobility were to preserve their lands by conversion to Islam, there were no local traditions to prevent such a scheme by necessitating the dispossession of former great landowners. The Seljuks, the Crusaders, and the Mongols in Asia Minor, the Catalans, the Bulgarians, the Serbians and the civil wars between the emperors in Macedonia and Thrace, the hangers-on of the Fourth Crusade in Thessaly, Greece, and the Aegaean Islands, had made so clean a sweep of the old aristocracy, attached to the soil, that Orkhan’s idea was feasible. Through these small holdings and through the rapid increase of conquered territory, the Ottoman sultans were able, almost from the beginning, to exercise an absolute sovereignty over their expanding dominions, and to prevent the rise of a class of nobles. The Ottoman Empire has never known an hereditary nobility. In the later conquests, the Sublime Porte sometimes granted life rights of governorship, with a tacit understanding that the succession should go to the son, to local chieftains or to large landowners. But these concessions were in regions never fully conquered, and remote from Constantinople. Those to whom these privileges were given had no part in the central government and no rank outside of their immediate locality. In place of military service, every adult Christian paid a special head-tax, to be used for the support of the army. The Christian was exempt from military service; the Mussulman was exempt from taxes.[142] This head-tax was heavy, and so gauged as to keep the Christian, unless he lived in a city, in economic dependence upon the Moslem landowner. As a general rule, during the first century and a half of Ottoman conquest, those who held to the old faith went to the cities and large towns. The Moslem thus became, without any attempt at forcible conversion or need to massacre, the undisputed possessor of the country districts.