Abu Bakr's successor Umar () curtailed the influence of the Qurayshite elite in favor of Muhammad's earlier supporters in the administration and military, but nonetheless allowed the growing foothold of Abu Sufyan's sons in Syria, which was all but conquered by 638. When Umar's overall commander of the province Abu Ubayda ibn al-Jarrah died in 639, he appointed Yazid governor of Syria's Damascus, Palestine and Jordan districts. Yazid died shortly after and Umar appointed his brother Mu'awiya in his place. Umar's exceptional treatment of Abu Sufyan's sons may have stemmed from his respect for the family, their burgeoning alliance with the powerful Banu Kalb tribe as a counterbalance to the influential Himyarite settlers in Homs who viewed themselves as equals to the Quraysh in nobility or the lack of a suitable candidate at the time, particularly amid the plague of Amwas which had already killed Abu Ubayda and Yazid. Under Mu'awiya's stewardship, Syria remained domestically peaceful, organized and well-defended from its former Byzantine rulers.