Abu Ubaidah ibn al-Jarrah
After the decisive Battle of Yarmouk, the Muslims marched northward deeper into Syria. After taking many small and large cities, both Abu Ubaidah ibn al-Jarrah and Khalid ibn al-Walid met at Qinnasarin, and they marched to Aleppo, where a strong garrison under a Roman general named Joachim held the fort. Aleppo consisted of a large walled city and a smaller but virtually impregnable fort outside the city atop a hill, a little more than a quarter of a mile across, surrounded by a wide moat.