Abu Ubaidah soon joined Khalid at Chalcis, which surrendered some time in June. With this strategic victory, the territory north of Chalcis lay open to the Muslims. Khalid and Abu Ubaidah continued their march northward and laid siege to Aleppo, which was captured after fierce resistance from desperate Byzantine troops in October. Before marching towards Antioch, Khalid and Abu Ubaidah decided to isolate the city from Anatolia. They accordingly sent detachments north to eliminate all possible Byzantine forces and captured the garrison town of Azaz, 50 kilometres (30 mi) from Aleppo; from there Muslims attacked Antioch from the eastern side, resulting in the Battle of Iron bridge. The Byzantine army, composed of the survivors of Yarmouk and other Syrian campaigns, was defeated, retreating to Antioch, whereupon the Muslims besieged the city. Having little hope of help from the Emperor, Antioch surrendered on 30 October, on the condition that all Byzantine troops would be given safe passage to Constantinople. Abu Ubaidah sent Khalid towards the north and he himself marched to the south and captured Latakia, Jablah, Tartus, and the coastal areas west of the Anti-Lebanon Mountains. Khalid moved north and raided territory up to as far as Kızılırmak River in Anatolia. Emperor Heraclius had already left Antioch for Edessa before the Muslims arrived. He then arranged for the necessary defenses in Jazirah and Armenia and left for Constantinople. On the way, he had a narrow escape when Khalid, who had just captured Marash, was heading south towards Manbij. Heraclius hastily took the mountainous path and, on passing through the Cilician gates, is reported to have said, "Farewell, a long farewell to Syria, my fair province. Thou art an infidel's (enemy's) now. Peace be with you, O, Syria – what a beautiful land you will be for the enemy hands."