خالد بن الوليد
He remained commander in chief of the Muslim army until Khalid ibn al-Walid arrived from Iraq to Syria in 634. Abu Ubaidah was ordered by Khalid ibn al-Walid to remain where he was until Khalid ibn al-Walid reached the Ghassanid city of Bosra, where they met. The castle surrendered the city after the Battle of Bosra in mid July 634 and 130 Muslims died in the battle.