The Arab certainly was not disposed to regard the conquered alien, even if he embraced Islam, as a brother. To him the conquest of foreign lands meant only the acquisition of vast estates, of great wealth and unlimited power: to him the conquered were simply serfs to be used as a means of rendering the conquered lands more productive. The conquered were allowed the choice either to embrace Islam or to pay the poll tax, but the 'Umayyads discouraged conversion as damaging to the revenue, although the cruel and hated Hajjaj b. Yusuf (d. 95) forced even converts to pay the tax from which they were legally exempt. (iii) The third stratum consisted of the "clients" (mawla, plur. mawâlî), the non-Arab converts, theoretically received as brethren and actually so treated by the "old believers," but regarded as serfs by Arabs of the Umayyad type. Owing to the wide expansion of Islam these rapidly increased in number until, in the 2nd century of the Hijra, they formed the vast majority of the Muslim world.
The two first Khalifs were "old believers" who had been companions of the Prophet in his flight from Mecca. The third, 'Uthman, had also been one of the Prophet's companions, but he was a weak man and moreover, belonged to the 'Umayyad clan, which, as the aristocratic element in Mecca, was then in the ascendant and, unable to free himself from the nepotism which is an Arab failing, allowed the rich conquests of Syria, Egypt, 'Iraq, and Persia to become the prey of ambitious members of the clan and thus
