or literary innovations. Athamina holds Abu Ubayda was likely installed because Khalid and his large force of tribesmen from Arabia and Iraq, along with their families, presented a threat to the old-established, formerly Byzantine-allied, and militarily experienced Arab tribes of Syria, whose defection was considered vital by Umar to form a network of defense against the Byzantines. This motivated him to demote Khalid and disband his army, the remnants of which were transferred to the Sasanian front in Iraq. Ajnadayn and Damascus Soon the Muslims heard of a gathering of 90,000 Byzantine army (Eastern Roman army) at Ajnadayn, about southwest of Jerusalem. All the divisions of the Muslim army, about 32,000 in number, joined Khalid at Ajnadayn on 24 July 634. Under the command of Khalid ibn al-Walid the Muslims defeated the Byzantine army there on 30 July 634 at the Battle of Ajnadayn. After one week, Abu Ubayda, along with Khalid, moved towards Damascus. On their way to Damascus, they defeated another Byzantine army at the Battle of Yakusa in mid-August 634. Caloiis and Azrail, the governor of Damascus, led another army to stop Khalid's corps but they were also defeated in the battle of Maraj-al-Safar on 19 August 634. The next day the Muslims reached Damascus and besieged the city, which continued for 30 days. After defeating the Byzantine reinforcements sent by Emperor Heraclius at the Battle of Sanita-al-Uqab, from Damascus, Khalid's forces attacked and entered the city. With Khalid's divisions investing the city from the northeast, Thomas, the purported son-in-law of the Emperor Heraclius, surrendered the city to Ubayda, who was besieging the Bab al-Jabiya (Jabiya Gate), on 19 September 634. Abu Ubayda was appointed by Khalid ibn al-Walid to siege the Jabiya Gate of Damascus. It was Abu Ubayda who gave peace to Damascus after Khalid ibn al-Walid attacked the city and conquered it by force. Abu Ubayda, Sharjeel ibn Hassana and 'Amr ibn al-'As, unaware of Khalid's attack from the Eastern Gate, gave peace to them, which was reluctantly endorsed by Khalid. The Byzantine army was given a cease fire of three days and allowed to go as far as they could with their families and treasure. Others simply agreed to stay at Damascus and pay tribute. The Muslims controlled the road to Emessa, so the Byzantines went west and then north up the Beqaa Valley. After the three-day truce was over, the Muslim cavalry,