The Muslims won a decisive victory at the Battle of Yarmouk fought in August 636, thus the attempt made by the Byzantine emperor Heraclius to roll back Roman Syria failed.
At this point, the rear elements of the besieging army were attacked by a Mobile guard led by Khalid ibn Walid, which in effect left the Byzantine forces devastated.
In the Autumn of 638, Abu Ubaidah launched several columns, including two commanded by Khalid ibn Walid and Ayadh, to raid Byzantine territory in Anatolia as far west as Tarsus.
[1] Khalid's objective was Germanicia (Arabic: Marash), the city which lies on a plain at the foot of the Taurus Mountains.
Many Muslim historians commented that Just the spoils of Marash were sufficient to make the soldiers of this expedition rich for life.