Freedmen; clients; the non-Arab converts to Islam.
Originally the term mawla (singular of mawali) referred to a party with whom one had an egalitarian relationship, such as a relative, ally, or friend, but the term eventually came to designate a party with whom one had an unequal relationship, such as master, manumitter, and patron, and slave, freedman, and client. Under the First Four Caliphs and the Umayyads, the influx of non-Arab converts to Islam created a new difficulty: how were they to be incorporated into tribal Arab society? The solution was the contract of wala', through which the non-Arab Muslim acquired an Arab patron. In principle, the mawali were to enjoy the same privliges as Arab Muslims; in practice they were regarded as inferior to the Arabs and were required to pay additional taxes. Despite such discrimination, the mawali rapidly rose to prominence in Muslim society in administration, military, and scholarship.
The Abbasid Revolution put an end to the political and social priviliges held by the Arabs. The institution of wala' as a requirement to enter Muslim society ceased to exist, but acquired political significance with the formation of troops entirely composed of freedman in the service of the caliph, a practice which persisted through the Ottoman period.