The greatest impact of Ottoman colonization in the Balkans, however, was felt in the urban centers. Many towns became major centers for Turkish control and administration, with most Christians gradually withdrawing to the mountains. Historical evidence shows that the Ottomans embarked on a systematic policy of creating new towns and repopulating older towns that had suffered significant population decline and economic dislocation during the two centuries of incessant wars preceding the Ottoman conquest, as well as the ravages of the Ottoman conquest itself. Often re-colonization of old towns and the establishment of new towns were accompanied by bodily transplanting settlers from other areas of the Empire or with Muslim refugees from other lands.