 Complete the following phrase:  The Syrian Desert, which extended from Balis to Ayla, had been inhabited by Bedouin nomadic Arab tribes since pre-Islamic times before mid-7th century. Throughout the 250 years following the Muslim conquest of Syria in the 630s, the Bedouin were brought under the authority of the Rashidun 632661, Umayyad 661750 and early Abbasid 750861 caliphates. However, during this period, certain Bedouin tribes also participated in Umayyad dynastic struggles, the 