Nothing further happened until the third week of August, during which the Battle of Yarmouk was fought. The battle lasted 6 days during which Abu Ubaida transferred the command of the entire army to Khalid. Outnumbered five-to-one, the Muslims nevertheless defeated the Byzantine army in October 636. Abu Ubaida held a meeting with his high command officers, including Khalid, to decide on future conquests, settling on Jerusalem. The siege of Jerusalem lasted four months, after which the city agreed to surrender, but only to Caliph Umar Ibn Al Khattab in person. Amr ibn Al As suggested that Khalid should be sent as Caliph, because of his very strong resemblance to Caliph Umar.