<P> Expansion ceased and the central disciplines of Islamic philosophy, theology, law and mysticism became more widespread and the gradual conversions of the populations within the empire occurred . Significant conversions also occurred beyond the extents of the empire such as that of the Turkic tribes in Central Asia and peoples living in regions south of the Sahara in Africa through contact with Muslim traders active in the area and Sufi orders . In Africa it spread along three routes, across the Sahara via trading towns such as Timbuktu, up the Nile Valley through the Sudan up to Uganda and across the Red Sea and down East Africa through settlements such as Mombasa and Zanzibar . These initial conversions were of a flexible nature . </P> <P> The reasons why, by the end of the 10th century, a large part of the population had converted to Islam are diverse . According to British - Lebanese historian Albert Hourani, one of the reasons may be that </P> <P> "Islam had become more clearly defined, and the line between Muslims and non-Muslims more sharply drawn . Muslims now lived within an elaborated system of ritual, doctrine and law clearly different from those of non-Muslims . (...) The status of Christians, Jews and Zoroastrians was more precisely defined, and in some ways it was inferior . They were regarded as the' People of the Book', those who possessed a revealed scripture, or' People of the Covenant', with whom compacts of protection had been made . In general they were not forced to convert, but they suffered from restrictions . They paid a special tax; they were not supposed to wear certain colors; they could not marry Muslim women; ." </P> <P> It should be pointed out that most of these laws were elaborations of basic laws concerning non-Muslims (dhimmis) in the Quran . The Quran does not give much detail about the right conduct with non-Muslims, in principle recognizing the religion of "People of the book" (Jews, Christians, and sometimes others as well) and securing a separate tax from them inlieu of the zakat imposed upon Muslim subjects . </P>

Focus was on trade eventually converted to islam