«(...) Historian Speros Vryonis observes that “since the beginning of the Arab razzias [raids] into the land of Rum [the Byzantine Empire], human booty had come to constitute a very important portion of the spoils.” As they steadily conquered more and more of Anatolia, the Turks reduced many of the Greeks and other non-Muslims there to slave status: “They enslaved men, women, and children from all major urban centers and from the countryside where the populations were defenseless.” The Indian historian K. S. Lal states that wherever jihadists conquered a territory, “there developed a system of slavery peculiar to the clime, terrain and populace of the place.” When Muslim armies invaded India, “its people began to be enslaved in droves to be sold in foreign lands or employed in various capacities on menial and not-so-menial jobs within the country.” (...)
Besides being practiced more or less openly today in Sudan and Mauritania, there is evidence that slavery still continues beneath the surface in some majority-Muslim countries as well -- notably Saudi Arabia, which only abolished slavery in 1962, Yemen and Oman, both of which ended legal slavery in 1970, and Niger, which didn’t abolish slavery until 2004. In Niger, the ban is widely ignored, and as many as one million people remain in bondage. Slaves are bred, often raped, and generally treated like animals. (...)»
 Speros Vryonis, The Decline of Medieval Hellenism in Asia Minor and the Process of Islamization from the Eleventh through the Fifteenth Century, Berkeley, 1971. P. 174-5. Quoted in Bostom, Legacy of Jihad, p. 87.  K. S. Lal, Muslim Slave System in Medieval India, Aditya Prakashan, 1994. P. 9.