In the North, the spread of Islam was slower due to the resistance of the Roman Catholic Church and the region's mountainous terrain. In the center and south, however, Catholicism was not as strong and by the end of the 17th century the region had largely adopted the religion of the growing Albanian Muslim elite. The existence of an Albanian Muslim class of pashas and beys who played an increasingly important role in Ottoman political and economic life became an attractive career option for most Albanians. Widespread illiteracy and the absence of educated clergy also played roles in the spread of Islam, especially in northern Albanian-inhabited regions. During the 17th and 18th centuries Albanians converted to Islam in large numbers, often under sociopolitical duress experienced as repercussions for rebelling and for supporting the Catholic powers of Venice and Austria and Orthodox Russia in their wars against the Ottomans.