 With the Byzantine army shattered and routed, the Muslims quickly recaptured the territory that they conquered prior to Yarmouk. The Muslim forces moved south to a last Byzantine stronghold, Jerusalem, where many of the Byzantine survivors of the disaster at Yarmouk took shelter. The Siege of Jerusalem lasted four months after which the city agreed to surrender, but only to the caliph in person. Amr ibn al-Aas, one of the four corps commander, suggested that Khalid should be sent as caliph, because of his very strong resemblance with Caliph Umar. Khalid was recognized and eventually, Umar came and Jerusalem surrendered in April 637. After Jerusalem, the Muslim armies broke up once again. Yazid ’ s corps came to Damascus and captured Beirut. Amr and Shurhabil ’ s corps went on to conquer the rest of Palestine, while Abu Ubaidah and Khalid, at the head of a 17,000 strong army moved north to conquer whole of the Northern Syria.
