"In the hours of its political degradation, Islam has achieved some of its most brilliant spiritual conquests: on two great historical occasions, infidel barbarians have set their feet on the necks of the followers of the Prophet, - the Saljūq Turks in the eleventh and the Mongols in the thirteenth century,- and in each case the conquerors have accepted the religion of the conquered. Unaided also by the temporal power, Muslim missionaries have carried their faith into Central Africa, China and the East India Islands."