How did Islam grow so quickly for so long?
Other methods have been employed by Mohammedans for propagating their faith, such as the purchase or forcible seizure of non-Moslem children in times of plague, famine, war and massacre, or even in times of no special disturbance, and rearing them in the Mohammedan faith. The Janissaries at Constantinople are a case in point. The children of Christians were taken regularly to replenish the ranks of this special body-guard of successive Sultans of Turkey. Another method employed to increase the number of Moslems was the plurality of wives and the use of captive women of non-Moslem races as concubines. These two methods of propagation were conspicuously employed[.]
--James Levy Barton
