"It is said that the Companions said a takbir (Allahu Akbar - Allah is the Greatest!) one day during the siege of Homs (Emessa), by which the town shook, such that some of its walls split asunder. Then they said another takbir, upon which some houses collapsed. Hence the public went to their leaders and said, "Do you not see what has befallen us, the situation in which we are? Will you not make peace with them for us?" So they made peace with them upon terms similar to those of Damascus …"1
In early March 635 (early Muharram, 14 Hijri), Abu Ubaidah and Khalid set off from Fahl to carry the war to the north. They had waited at Fahl while Shurahbil was dealing with Baisan and Tabariya, in case a large scale battle should develop necessitating their participation. Once Tabariya was taken, the possibility of such a battle in Jordan vanished and they were free to depart.
A few miles west and south west of Damascus stretched a grassy plain known in Muslim history as Marj-ur-Rum, i.e. the Meadow of Rome, and towards this plain Abu Ubaidah and Khalid moved with the intention of bypassing Damascus and continuing the advance to Emessa. Yazeed was still in peaceful occupation of Damascus and would remain there a few months yet, before receiving orders from Umar to operate against the Mediterranean coast. At Marj-ur-Rum, Abu Ubaidah again made contact with sizable Roman forces.
On hearing of the Muslim operations at Baisan and Tabariya, Heraclius surmised that the Muslims had chosen Jordan and Palestine as their next strategic objectives and were not interested in Northern Syria. He also heard that only a weak corps of the Muslim army remained at Damascus, and this corps was showing no sign of aggressive intent. He therefore determined to retake Damascus rapidly. With this object in view he sent a Roman force under a general named Theodorus to fight and defeat the Muslim garrison in Damascus and re-occupy the city. This force set off from Antioch, and moving via Beirut, approached Damascus from the west. This movement, however, had hardly begun when Heraclius was informed that Abu Ubaidah and Khalid had left Fahl and were moving north again. They would arrive at Damascus at about the same time as Theodorus, and the Romans would then not have a chance to retake the city. To strengthen the Roman force, Heraclius ordered the detachment of a part of the large garrison of Emessa to reinforce Theodorus. This detachment, under the command of Shans, marched from Emessa on the direct route to Damascus.
The Muslims arrived at Marj-ur-Rum to find Theodorus waiting for them. On the same day Shans also arrived from Emessa and the two armies deployed in battle formation facing each other. In this deployment Abu Ubaidah stood opposite Shans while Khalid stood opposite Theodorus. The strength of the Roman forces here is not known, but it may be assumed that it amounted roughly to two strong corps. It could not have been much less otherwise it is doubtful if the Romans would have accepted battle with the two Muslim corps facing them. For the rest of the day the two armies remained in their battle positions, each waiting for the other to make the first move.
As night fell, Theodorus decided to carry out a skilful strategical manoeuvre. Leaving Shans to face the Muslims, he pulled back his corps under cover of darkness, moved it round the flank of Khalid and by dawn on the next day arrived Damascus. His intention was to keep the main Muslim army busy at Marj-ur-Rum with the corps of Shans, while with his own corps he quickly destroyed the Muslim garrison of Damascus. It was a very clever plan, and the movement was carried out with such perfect organization that it was not until the latter part of the night that the Muslims came to know that half the Roman army facing them was no longer there.
At Damascus, Yazeed's scouts brought word at dawn of the coming of the Romans. On receiving this news, Yazeed immediately deployed his small corps outside the fort facing south-west. Feeling more at home in the open and unused to being besieged in a fort, the Muslims preferred to fight in the plain rather than in the city. Just after sunrise began the battle between Theodorus and Yazeed and soon the Muslims found themselves hard pressed, for the Roman force vastly outnumbered them. But they held their own till about mid-morning. Then, just as the situation had become desperate for Yazeed, the Romans were struck in the rear by a furious mass of Muslim horsemen. This was the corps of Iraq, spearheaded by the Mobile Guard. In a very short time Khalid and his fearless veterans, attacking from the rear, had chopped the Roman corps to pieces. Few Romans escaped the slaughter, and Khalid killed Theodorus in a duel. A large amount of booty, mainly weapons and armour, fell into Muslim hands and was shared by the warriors of Khalid and Yazeed, except for the usual one-fifth reserved for Madinah.
1. Ibn Kathir, Al-Bidayah wan-Nihayah, Dar Abi Hayyan, Cairo, 1st ed. 1416/1996, Vol. 7 P. 65.