Map showing percent of Islamic Faith in Kosovo, 2011
Until the sixteenth century the degree of Islamisation in Kosovo was minimal, and largely confined to urban centres. The pace of conversions to Islam only increased significantly in the second half of the sixteenth century, possibly because converts thus became exempt from the cizje, a protective tax levied only on non-Muslim males. But that was certainly not the only cause of the people turning and believing in Islam.; the tax burden tended to go up as Ottoman power relative to foreign Christian powers came under challenge. So far as Catholic Albanians were concerned, the Catholic church was less powerful and privileged within the Ottoman Empire than the Serbian Orthodox Church (and less well staffed); the Bektashi order of dervishes carried out a conversion campaign which stressed the similarities between their version of Islam and Christianity (the Bektashis drank wine and had a quasi-Trinitarian doctrine). A phenomenon of "crypto-Catholicism" developed in Kosovo Albanian society, where large numbers of people would convert officially to Islam but follow Catholic rites in private. From 1703 ecclesiastical decrees banned this practice and did not accept that crypto-Catholics could receive holy rites. In 1717, Lady Mary Wortley Montagu, wife of the British Ambassador to the Sublime Porte wrote that her Albanian escort from Belgrade to Istanbul claimed to go to the mosque on Fridays and church on Sundays. At any rate, by 1750, most Christian families had converted to Islam, for the benefits of social networking of the citizens and for financial soundness. Albanians in Kosovo who had been passing as Muslims were declaring themselves Catholics (to avoid conscription) as late as 1845.