The marvellous victories of Khalid bin AI-Waleed in `Iraq encouraged Abu Bakr to send armies to conquer Syria. The Arabs had a good knowledge of this country because of their continual land trade with it. There were two main reasons why they decided to wage a daring ¹  war against what was then the greatest empire in the world:

a) the spreading of Islam, and
b) the wealth of Syria.

When Abu Bakr sent Khalid bin Sa'id at the head of an army to Tayma', just near the Syrian border, he did not intend to invade the country; it was only a defensive measure. But when he received letters from Khalid bin Sa'id, who longed for military glory in Syria as great as that of Khalid bin Al-Waleed in `Iraq, asking for permission to proceed, he could not stand the temptation and gave the signal which started a new holy war.

In his first engagement with the Romans, Khalid bin Sa'id managed to win the battle and occupy the Roman camps. Tasting victory against "the people of the yellow complexion", as they were usually described by the Arabs, Khalid pushed forward till he reached the shores of the Dead Sea, where he defeated another Roman regiment near Qastal.

Now, the Romans realized that the Muslims were not merely indulging  ²  in temporary raiding  ³ , as they used to do before, but that they intended to conquer and stay. So they sent a huge army led by Bahan, who was well-known for his clever military tactics ⁴ . He withdrew intentionally before Khalid, who forgot Abu Bakr's piece of advice to be always wary in his war with the Romans. Bahan's retreat stopped when he was in the vicinity of Tiberias. There he managed to trap the Muslims and kill Khalid's son, Sa'id, who was lagging behind ⁶  with a group of his men.

 The bad fortune which befell ⁹  Ibn Sa'id did not make Abu Bakr despair. He ordered the recruitment of new troops and immediately sent aid to 'Ikrimah, who was waiting near the Roman !order. The total aid which `Ikrimah received amounted to 30,000 men. `Amr bin AI-'As had to proceed to Palestine, Abu `Obaydah bin AI-Jarrah to Damascus, Shurahbeel bin Hasnah to Jordan and Yazeed bin Abu Sufyan to Busra.

 When Heraclius, the Roman emperor, heard the news, he mustered ¹⁰  about 240,000 troops. Theodore, his brother, led the huge army and proceeded to Waqusah, some 40 miles to the south of Yarmuk, a tributary of the Jordan. He camped beside the left bank of the river on a spacious plateau ¹¹  which was surrounded on three sides by high mountains.

 At first the Muslim leaders acted separately; but when they realized the imminent ¹² danger, they sent for advice from the caliph, and meanwhile consulted the shrewd  ¹³ leader Amr bin Al- 'As. Both Abu Bakr and Amr recommended that the Muslims should unite. So, the four armies marched and camped on the right bank of the Yarmuk, just opposite the Romans.

 Two months passed without any action on either side because each was afraid of the other. Then Abu Bakr got bored and sent a message to Khalid bin Al Waleed in Al-Heerah ordering him to leave for Yarmuk. Khalid was unwilling to leave as he was hoping to conquer Mada'in very soon, but he had to carry out the caliph's orders. He chose his men, and at the head of some 9,000 men left 'Iraq for Syria.

He set out towards Doomat Al-Jandal, then went along the Sirhan valley. When he reached Qoraqir, he decided to take a longer and more dangerous route so as to avoid any confrontation with the enemy. Following the advice of his guide, Rafi bin `Ameerah, he made his camels go without water for a number of days, then he let them drink their fill. He tied up their ears and lips in order to prevent any evaporation ¹⁴  of water. Then he crossed the desert, and after five days arrived in Palmyra, just behind the armies of his opponents. Soon he joined his colleagues, who were anxiously waiting for him at Yarmuk.

 Khalid's arrival was offset  ¹⁵  by the arrival of Bahan, the Roman conqueror of Khalid bin Sa'id. Another month passed and still the Muslim emirs were acting separately, as Abu Bakr had not appointed an overall commander-in-chief. The Romans began to prepare for battle, and Khalid called for a council of war ¹⁶  First he let the other leaders speak, and when his turn came, he spoke zealously  ¹⁷  and suggested a genuine union of the five armies without which, he said, no victory could be achieved. Regarding the commander-in-chief, he pointed out that each leader might be given the post for one day, and that he himself would assume it first.

 They unanimously agreed to the suggestion, and Khalid divided the armies into companies each headed by a competent captain. Besides, there were people whose task was to encourage the fighters and raise their morale; one of them was Abu Sufyan, the Prophet's chief opponent in the battle of Badr. While the Muslims were getting ready to fight against the Romans one of them said, "Hownumerous the Romans are, and how few the Muslims are!" Khalid got angry and said, "The reverse  ¹⁸  is true! It is victory that makes the troops numerous, and defeat that makes them few!"

 Such an encouraging leader, and the enthusiasm of the Muslims to fight in the cause of God so as to attain Paradise, combined to make the men brave and even inspired the women to take part in the war.

 Among the Romans there was a captain called George, who had contacted Khalid before the battle and promised to defect. When the fight started, he was in the van, and when he reached the Muslims'lines Khalid gave way and let him pass through. The other Romans thought that George needed help, so they attacked the Muslims fiercely, which made them retreat.''Ikrimah bin Abu Jahl was at the head of a company of 400 strong. Seeing what had happened, he vowed martyrdom  ¹⁹ or victory and shouted: "Oh, that I should have fought the Prophet in so many battles only to run away from infidels!" He advanced, followed by his son Amr, Harith bin Hisham, Dhirar bin Al-Azwar and the rest of the company, and made the enemy retreat. As for George, having embraced Islam and said his prayers in Khalid's tent, he fought with the Muslims against his countrymen. In spite of the Romans' heroic fighting, at sunset their lines began to waver and then broke. In order to cut the battle short, and because the Romans were besieged from all sides, Khalid allowed the enemy's cavalry to escape. This being accomplished, he tightened  ²⁰  the siege on the infantry. Realizing that there was no chance of escape, the Romans began to retreat, only to fall into the river. Muslim historians estimate that between 100,000 and 120,000 enemy troops died at Yarmuk. With them about 3,000 Muslims also died, among whom were `Ikrimah and his son `Amr. They were brought to Khalid in Theodore's tent and their heads laid on his lap. He wiped their faces gently with a damp ²¹  cloth and dripped22 water in their mouths hoping they might revive, but his attempts were futile and both of them died. As for Abu Sufyan, whose loud voice had urged many a Muslim to war, he had one of his eyes pierced by an arrow, which was pulled out by a skilled man called Abu Hathmah.

 It should be mentioned here that the news of Abu Bakr's death arrived while the battle of Yarmuk was raging. On becoming caliph, the first thing `Omar bin al-Khattab did was to send a message to Syria deposing Khalid from the general leadership and appointing Abu `Obaydah to the post. Yet, when the latter received the message, he concealed  ²³  it from everyone and did not show it to Khalid till the Muslims advanced from Yarmuk and laid siege to Damascus. Khalid's remark at the new caliph's order was: "I am fighting in the cause of God, not for 'Omar bin al-Khattab."

When Heraclius heard of his brother's defeat at Yarmuk he left Homs, the imperial headquarters, and moved northwards. There he mustered a new army, which was met by the Muslims and also defeated.

As for the Muslims, they first took Jordan from the Romans and then laid siege to Damascus, which was heavily fortified. The inhabitants resisted the Muslims from behind their walls, and at the same time urged the emperor to send them reinforcements. Heraclius made one attempt to help them, but finding it futile stopped all further attempts. History books still quote the emperor's words of farewell, "Good-bye, Syria! I do not think we shall meet again."

 It was not long before Damascus opened two of its gates to the Muslims, one forced by Khalid, and the other opened peacefully by Abu `Obaydah. With the capital in the hands of the Muslims, and wit the Romans driven out for ever, Syria became an Islamic country.