The Battle of Marj ar-Rum, also known as the Battle of Marj Dimashq, was a conflict between the Rashidun caliphate and the Byzantine Empire. The battle occurred shortly after the Battle of Fahl when the Byzantines attempted to recapture Damascus. Heraclius, the Byzantine emperor, sent two separate forces in the effort, one army led by Theodore the Patricius and a second army led by Shannash al-Rome. The Rashidun army led by Abu Ubaydah ibn al Jarrah and Khalid ibn al-Walid was ordered to assist Yazid ibn Abi Sufyan who was acting as the garrison commander of Damascus.