Banu Kalb
As a result of the deaths of his top commanders in Syria, Umar appointed Yazid's brother and deputy, Mu'awiya ibn Abi Sufyan, commander of the army there, ultimately laying the foundation for the establishment of the Syria-centered Umayyad Caliphate by Mu'awiya in 661. The historian Wilferd Madelung surmises that the plague in Syria had precluded Umar from deploying commanders more preferable to him from Medina and he thus appointed Mu'awiya in lieu of a suitable alternative. The losses among the Muslim troops in Syria caused by the Amwas plague contributed to Mu'awiya's heavy military reliance on older-established, formerly Byzantine-allied and Christian Arab tribes in Syria, particularly the Banu Kalb, who had largely stayed neutral during the fighting between the Muslims and the Byzantines in Syria during the 630s.