The Battle of Yarmouk

The Battle of Yarmouk (also spelled Yarmuk, Yarmuq or Hieromyax )
Date August, 636
Location Near the Yarmouk River
Result Decisive Muslims victory
Territorial changes Levant annexed by Rashidun Caliphate
Combatants :Byzantine Empire,Ghassanid Kingdom,Kingdom of Armenia,Georgia,Slavic and Frankish allies / Rashidun Caliphate (Rashidun army)
Commanders : Heraclius Constantine III[1] Theodorus Trithurius[2] Jabalah VI ibn aI-Aiham Dairjan[3] Vahan[2] (Mahan[3]) Buccinator (Qanateer)[3] Gregory[3] / Khalid ibn al-Walid ,Abu Ubaidah ibn al-Jarrah ,Amr ibn al-A'as ,Shurahbil bin hassana ,Yazid ibn Abu Sufyan
Strength : 100,000 - 400,000 / 7,500 - 40,000
Casualties : 50,000 killed (modern estimate)[9] 45% killed (modern estimate)[3] 70,000 - 120,000 killed(primary sources) / 4,000 killed

The epic Battle of Yarmouk (also spelled Yarmuk, Yarmuq or Hieromyax) took place between the Rashidun Caliphate and the Byzantine Roman Empire over 6 days in August 636. It is considered by some historians to have been one of the most significant battles in the history of the world, in that it marked the first great wave of Muslim conquests outside the Arabian Peninsula. It also heralded the rapid advance of Islam into then Christian Palestine, Syria and Mesopotamia. This battle is also considered to be one of Khalid ibn al-Walid's most decisive victories, and cemented his reputation as one of the greatest military strategists and cavalry commanders of the Medieval Ages.

The Battle of Yarmouk took place only four years after Muhammad(SAW) died in 632. It was conducted under the auspices of his successor, the second Caliph, Umar.

Damascus had once been a stronghold of the Byzantine Empire. In 634 Rashidun army invaded Syria, and, after raids and skirmishing, captured Damascus in 634. From there, the Muslims continued their conquest across the Levant. Soon after the conquest of Damascus, the Muslims decisively defeated the Byzantine armies at the Battle of Ajnadayn, the Battle of Fahl and, finally, the Battle of Yarmouk.

After previous incursions from Rashidun army, the Byzantine emperor Heraclius decided to assemble a grand army in Syria to roll back the Arab invasion. Preparations started in late 635, and by May 636 a force was put under arms and was concentrated at Antioch and northern Syria. The size of these forces was stated as 100,000 to 200,000 in most Muslim accounts of the battle, but several modern estimates suggest that the real number of troops was in the lower end of that range. See, for example, [11] who reckon the count at 100,000 [12][13] 80,000,[2] or 50,000.[14] The assembled army consisted of contingents of Romans, Greeks, Slavs, Franks, Georgians, Armenians and Christian Arabs,[15] contributing to internal conflicts.

This force was organized into five armies, whose commanders were: Mahan,[16] King of Armenia who commanded a purely Armenian army; Qanateer, a Slavic prince commanded all the Slavs; Jabla bin AI Eiham, King of the Ghassanid Arabs, commanded an exclusively Christian Arab force. The remaining contingents (all European) were placed under Gregory and Dairjan.[17] Mahan was appointed Commander-in-Chief of the entire Imperial army.

At this time the Rashidun army were split in four groups: Amr bin Al Aas in Palestine, Shurahbil in Jordan, Yazeed at Caesarea, and Abu Ubaidah ibn al-Jarrah along with Khalid ibn al-Walid at Emesa. Heraclius sought to exploit this situation and planned to attack and destroy each of these Muslim corps separately, one at a time, by putting a large concentration of troops against each of them in turn. So reinforcements were sent to Caesarea under Heraclius?s son Constantine, probably to tie down Yazeed?s forces there so that it would not move to join other Muslim?s corps to help them. The rest of the Imperial Army was to operate on the following plan:

Qanateer would move along the coastal route up to Beirut, then approach Damascus from the west and cut off Abu Ubaidah.

Jabla would march from Aleppo on the direct route to Emessa via Hama, and hold the Muslims frontally in the Emessa region. The lighter-armed but faster moving Christian Arabs would thus be the first to contact the Muslim Arabs.

Dairjan would move between the coast and the Aleppo road and approach Emessa from the west, thus striking the Muslims in their flank while they were held frontally by Jabla.

Gregory would advance on Emessa from the north-east and attack the Muslims in their right flanks at the same time as they were struck by Dairjan.

Mahan?s army would advance behind the Christian Arabs and act as a reserve.[18]
The Imperial Army was launched from Antioch and Northern Syria some time in the middle of June 636 A.D. It was at Shaizar, through Roman prisoners, that the Muslims first came to know of the preparations being made by Heraclius. Alert to the possibility of being caught with separated forces that could be destroyed in detail, as Heraclius indeed planned, Khalid ibn al-Walid advised Abu Ubaidah ibn al-Jarrah to pull back from North and Central Syria, as well as from Palestine, and concentrate the whole army so that a strong, united force could be fielded against the Byzantine armies, and in case of retreat the Arabian Desert will not be too far.[19]. Abu Ubaidah ibn al-Jarrah thus ordered the commanders to give up the territory under their control and withdraw the army to Jabiya. He also ordered the commanders to return the Jizya (tribute) to the people who had paid it.[20].

In the middle of July 636 AD in a council of war Khalid bin Walid gave his plan to Abu Ubaidah ibn al-Jarrah, the commander in chief of the Muslim?s army.

? ?"Know, O Commander, that if you stay at Jabiys, you will be helping the enemy against you. In Caesarea, which is not far from Jabiya, there are 40,000 Romans under Constantine, son of Heraclius.[21] I advise you to move from here and place Azra behind you and be on the plain of Yarmuk. Thus it would be easier for the Caliph to send reinforcements and ahead of you there would be a large plain, suitable for the charge of cavalry."[22]. ?

The Rashidun army moved towards the yarmuk plain during which there was a skirmish between Khalid's mobile guard and Byzantine cavalry, Khalid routed the advance guard of Byzantine. The Muslims established a line of camps in the eastern part of plain of yarmuk. Here Abu Ubaidah was joined by the corps of Shurahbil, Amr ibn al-A'as and Yazeed.

A few days later the Byzantine army, proceeded by the lightly armed Christian Arabs of Jabla, moved up and established their camps just north of the Wadi-ur-Raqqad.

Heraclius Instructed Mahan, the commander in Chief of the imperial army, not to start battle until all avenues of peaceful negotiation had been explored. Mahan sent Gregory to hold talks with Muslims if they would agree to retire to Arabia and not come back again but he failed, later Jabla was sent but no results came. Before the Battle, on Mahan?s invitation Khalid also went to hold talks but still no result.[23] Caliph Umar sent the reinforcement of 6,000 troops, mostly from Yemen. Though most scholars agree that the Muslim army was largely outnumbered by the Roman army. But the morale of the Muslim army was very high as it included 1,000 companions of Muhammad (SAW), and these in turn included 100 veterans of the Battle of Badr, the first battle of Islam. The army also included citizens of the highest rank, such as Zubair,[24] Abu Sufyan, and his wife Hind bint Utbah.[25]

Modern estimates for the size of respective armies vary, between 15,000 - 100,000 for the Romans, and 7,500 - 25,000 for the Muslims, claiming exaggerations on both sides by older historians. These figures come from studying the logistical capabilities of the combatants, the sustainability of their respective bases of operations, and the overall manpower constraints affecting the Romans and Arabs. Most scholars, however, agree that the Romans and their allies outnumbered the Muslim Arabs by a sizable margin.

Muslim sources place the number of Muslim troops to be between 24,000 and 40,000 and Byzantine forces to be between 100,000 and 200,000.

Byzantine Roman army:
Mahan deployed the Imperial Army forward of Allan. He used his four regular armies to form the line of battle, extending from the Yarmuk to south of the Hill of Jabiya. The right wing was commanded by Gregory and on his left the army of Qanateer. The centre was formed by the army of Dairjan and the Armenian army of Mahan-both under the command of Dairjan. The Roman regular cavalry was distributed equally among the four armies, and each army deployed with its infantry holding the front and its cavalry held as a reserve in the rear. Ahead of the front line, across the entire 12-mile front, Mahan deployed the Christian Arab army of Jabla, which was all mounted-horse and camel. This army acted as a screen and Skirmish line, until they would be joined by the main army. The army of Gregory, which formed the right wing, used chains to link its foot soldiers.[26]. All these foot soldiers had taken the oath of death. These chains were in 10-men lengths, and were used as a proof of unshakeable courage on the part of the men who thus displayed their willingness to die where they stood and not retreat. The chains also acted as an insurance against a break-through by enemy cavalry.

Muslim Arab army:
During a council of war Khalid ibn Walid, who was conqueror of Iraq and a former commander in chief of the Rashidun army in the campaign of Syria,[27] offered his services as a commander of the Muslim army until the battle was over, and indeed command of the Muslim army was given to him that day. Abu Ubaidah ibn al-Jarrah was a respected man, but his military prowess was not like that of Khalid ibn Walid.[28]. After taking command. Khalid reorganized the army into infantry and cavalry regiments, with cavalry making up a quarter of the army (10,000 cavalry out of the 40,000 figure). Khalid further divided the army in to 36 infantry regiments and four cavalry regiments of which mobile guard was held in reserve. Over the course of the battle Khalid would repeatedly make critical, decisive use of this mounted reserve. The army was lined over a front of 11 miles, with its left on Yarmouk River a mile before the ravine began and right on Jabiya road. The Center of the army was under the command of Abu Ubaidah ibn al-Jarrah (left half) and Shurhabeel bin Hassana (right half). The left wing was under the command of Yazeed and the right wing was under Amr ibn al-A'as. Both left and right wings were given the cavalry regiments under command, to be used as a reserve for counter attack in case they were pushed back by the Byzantines. Behind the center stood the one cavalry regiment reserve along with a mobile guard under the personal command of Khalid. When Khalid was busy in the conduct of the battle Zirrar ibn al-Azwar would command the mobile guard. The commanders of the other three cavalry regiments were Qais bin Hubaira, Maisara bin Masruq and Amir bin Tufail. Each of the four corps had nine infantry regiments, which were all formed on a tribal and clan basis, so that every man would fight next to well-known comrades, and the army pushed out a line of scouts to keep the Byzantines under observation.[29]

In late July 636 AD, Mahan sent Jabla with his Christian Arabs forces to check the strength of the Muslim front, but before Jabla could reach the Muslim front, Khalid attacked with his mobile guard and drove back Jabla's corps.[30].After this initial operation nothing happened for a month.

The battlefield lies about 40 miles from the Golan heights currently a disputed upland region on the frontier between Israel and Syria, northeast of the Sea of Galilee.[31].

It was Khalid ibn al-Walid who manoeuvered to choose this field of battle, because he judged it most useful for cavalry operations, and because it allowed a clear line of retreat to Arabia. The battlefield which stretched between the two camps consisted of the Plain of Yarmouk which was enclosed on its western and southern sides by deep ravines, known as Wadi-ur-Raqqad with banks about 1,000 feet deep. This ravine joins the Yarmouk River on its southern side. On the south of the battlefield lies the Yarmouk River, a tributary of River Jordan, this stream has very steep banks from 300-1,000 feet deep.[3].On the northern side of the battlefield lies the Jabiya road and to the east lie the Azra hills, although these hills were outside the actual field of battle.

There was only one prominence in the battlefield: a 300 feet high elevation known as the hill of Jamu'a(gathering), because part of Muslim's corps was concentrated over it, as it gives a good view of the plain of Yarmouk. In 636 AD The ravine at the west of the battlefield was crossable at a few places but there was only one main crossing, at a ford, where the village of Kafir-ul-Ma stands today.[3]

The battle begun in the third week of August 636. At dawn both armies lined up for battle and were a little less than a mile apart.

Day 1:
At midday one-third of the infantry of each of the four corps of the Byzantine army advanced to battle. They were subjected to intense archery, which caused significant casualties and soon both sides were locked in combat.

The Roman assault was not a determined one, Mahan had attempted a limited offensive on a broad front to test the strength and strategy of the Muslim army, and if possible, achieve a breakthrough wherever the Muslim front was weak. Many of the soldiers of the Imperial army were unused to battle and were unable to press the attack as the Muslim veterans did. On some parts of the front the fighting was more violent than on others, but on the whole the action of this day could be described as steady and moderately hard.[32] The Muslims held their own. The Romans did not reinforce their forward infantry, and at sunset the action ended with the two armies separating and returning to their respective camps. Casualties were light on this day, though higher among the Byzantines than the Muslims.[3]

Day 2:
Mahan in a council of war decided to launch his attack at dawn, so that the Muslims would be caught unprepared. He ordered the preparation of attack during the hours of darkness, his plan being to engage the two of his central armies with the Muslim's central armies to tie them down while the main thrusts would be against the wings of the Muslim army, which would then be either driven away from the battlefield or pushed in to the center. To observe the battlefield Mahan had a large pavilion built behind his right wing with a bodyguard of 2000 Armenians. He ordered the army to prepare for the surprise dawn attack.[3]

The Byzantines attacked soon after dawn and the Muslims were caught probably unprepared, but Khalid had already placed a strong outpost line in front during night, which gave the Muslims time to prepre for battle. The sun was not yet up on this second day of battle when the two armies clashed.[3]At the center, the Byzantines were not pressing hard as this was meant to be a limited attack to pin these Muslim central corps in their position.[33]Thus the centre remained stable. But on the right wing of the Byzantine army, the Slavic prince Qanateer, commanding a force of mainly Slavs, attacked and forced the Muslim infantry to retreat, after which Amr ibn al-A'as ordered his cavalry regiment to counter attack, which checked the Byzantine advance and stablizied the battle line.

The situation on the Muslim left wing was only a little less serious. Here too the Byzantines broke through the corps of Yazeed. This was the army of Gregory, with chains, more slow-moving than the others but also more solid. Yazeed too used his cavalry regiment to counter attack but it was repulsed; and after a period of stiff resistance the warriors of Yazeed fell back to their camps but afterwards managed to hold a stable line.

Mahan's plan appeared to be succeeding. The centre of the Muslim army was pinned down and its flanks had been pushed back. But although they had been forced back, neither flank had broken. It was now about midday, and Khalid decided to use his mobile guard to assist the wings in counterattacks to re-establish their battle positions.

Khalid first turned to the right wing and with his mobile guard and reserve cavalry regiment of right wing, struck at the flank of the army of Qanateer at the same time as Amr counter-attacked again from the front. Simultaneously attacked from two sides, the Slavs very soon turned and beat a hasty retreat to their original position. Amr regained all the ground that he had lost and started to reorganize his corps for the next round.

As soon as this position on his right was restored, Khalid turned to the left wing. By now Yazeed had begun a major counter attack from the front to push the Romans back. He was up against the formidable chained Byzantine infantry of Gregory. Khalid detached one regiment under Zirrar ibn al-Azwar and ordered him to attack the front of the army of Deirjan (left half of the center) in order to create a diversion and threaten the withdrawal of the Roman right wing from its advanced position. With the rest of the mobile guard Khalid then attacked the flank of Gregory. Here again, under simultaneous attacks from front and flank, the Romans fell back, but more slowly because with their chains the men could not move as fast.[34] A critical blow to Byzantine morale arrived while the Roman right was falling back. Zirrar ibn al-Azwar broke through the army of Deirjan and killed him. At sunset the central armies broke contact and withdrew to their original positions and both fronts were restored along the lines occupied in the morning. Again, the Byzantine army had suffered slightly higher casualties than the Muslim army, but the death of Deirjan and the failure of Mahan's battle plan left the Imperial army relatively demoralized, whereas Khalid's successful counterattacks emboldened his troops.[3]

Day 3:
After the failure of the previous day's ambitious battle plan, and the loss of one of their senior commanders with the death of Deirjan, Mahan's Imperial Byzantine army decided for a less ambitious plan, aiming to break the Muslim army at a specific point: the junction between the centre of the Muslim army and its right flank. Qanateer's Slavs would lead the charge. Thus battle on this day began with a Byzantine attack on the corps of Amr ibn al-A'as on the right wing and Sharhabeel bin Hasana, who commanded the right hand side of the centre of the Muslim army, selecting as the main point of attack the junction between Sharhabeel and Amr bin Al Aas.

The initial attacks were repulsed by the Muslims but soon the numerical advantage of the Byzantine army begin to tell and the Muslim right wing retreated toward their base camps followed by the retreat of the right half of the Muslim?s center under the command of Sharhabeel bin Hasana.[35] But this day the retreat was not as severe as that of the previous day, and the corps reorganized some distance from the Muslim camp for a counter attack.[36]

Now again Khalid intervened decisively, launching his mobile guard against the left flank of Qanateer's corps (right half of Byzantine army's center). At the same time Amr's cavalry regiment maneuvered from the right and struck at right flank, while the infantry of Amr and Sharhabeel counter-attacked frontally. This time the combat was severe. Many on both sides fell in combat but by dusk the Byzantines had been pushed back to their own position and the situation restored as at the beginning of the battle

Day 4:
The fourth day was going to prove decisive, and both army commanders knew it. Mahan decided to persist with the previous day's war plan, judging that the right wing of the Muslim army had suffered a lot so far.

With this plan of battle, the two armies of Qanateer (right wing and right half of the central corps Armenians and slavs respectively) were set in motion against the corps of Amr and Sharhabeel. Amr was pushed back again, but not as far as on the previous day. Some distance behind its original position, the corps of Amr held the Byzantine Slavs and intense fighting started there. In the sector of Sharhabeel, however, the Armenians broke through and pushed the Muslims back towards their camp. The Armenians were strongly supported by the mounted Christian Arabs of Jabla, and this proved the most serious penetration of the Muslim front.

Once again, Khalid bin Walid decisivley entered the fray with his mobile guard.

Khalid feared a general attack on a broad front, in which case it could be impossible for him to repulse the Byzantine advance with his mobile guard, and he therefore ordered Abu Ubaidah and Yazeed to attack the Byzantine corps on their respective fronts. The purpose of the attack was just to tie down the Byzantine right half of the center and right wing and pre-empt a general advance of the Imperial army.[38].

Khalid then decided to strike against the advancing Armenians on the right half of the central corps. He divided his mobile guard into two equal groups of which he gave one to Qais bin Hubeira and kept the other with himself. Leading his own cavalry group, Khalid galloped round behind the corps of Sharhabeel and appeared against the northern flank of the Armenians. Now began a three-pronged counter attack against the Armenians and Christian Arabs. Khalid from the right, Qais from the left and Sharhabeel from the front with his infantry. At last the Armenians fell back and retreated towards there own position. The operation against the Armenians lasted the whole afternoon.

As the Armenians pulled back, the Slavs of Qanateer, denied the support of the Armenians on their flank, also retired. The positions of Sharhabeel and Amr were now restored. While the operation on the Mulims right was taking place, a similarly intense fight was taking place on their left. With Khalid's reserve fully committed against the Armenians on the right sector, the left had to rely entirely on themselves. Khalid had ordered the corps of Abu Ubaidah and Yazeed to attack the Byzantines from their respective fronts to tie them down and prevent a general assault by the entire Byzantine army, but soon they were pushed back by intense Byzantine archery which caused heavy casualties. Many Muslim soldiers lost their sight to Byzantine arrows on that day, which thereafter came became famous by the name Day of lost eyes.[39]

The armies of Abu Ubaidah and Yazeed fell back, except the regiment of Ikramah bin Abu-Jahal, who was on the left of Abu Ubaidah's corps, and who called on his men to take an oath of death and not to retreat and to go down fighting. Four hundred men immediately responded and their attack impeded the Byzantine army. The suicidal act of Ikrimah?s regiment provided a cover for the retreating Arabs, who reorganized themselves and counter-attacked to regain their lost positions. All Four hundred of the dedicated men who had taken the oath of death were either killed or seriously wounded, but in the process killed many more than four hundred Byzantines. Ikrimah and his son, Amr, were mortally wounded.[40].

By dusk the day's action was over. Both armies stood once again on their original lines. Ikrimah and his son Amr, one of the childhood friends of Khalid ibn Walid, died that evening due to the wounds they got in their stand against the Byzantines. It had been a bloody day on which the Byzantines came very near to victory.

Day 5:
Early on the fifth day of battle the two armies were again formed up on their usual battle lines. One man emerged from the Byzantine centre. This was an emissary of Mahan who brought a proposal for a truce for the next few days so that fresh negotiations could be held. Abu Ubaidah ibn al-Jarrah nearly accepted the proposal but was restrained by Khalid ibn al-Walid. On Khalid's insistence he sent the envoy back with a negative reply, adding:[41]

? "We are in a hurry to finish this business!" ?

The rest of the day passed uneventfully. Khalid knew that the Byzantines were no longer eager for battle. Up till now the Muslim army had adopted a largely defensive strategy, but Khalid now decided to take the offensive and reorganized his troops accordingly. All the cavalry regiments were grouped together into one powerful mounted force with the mobile guard acting as its hard core. The total strength of this cavalry group was now about 8,000 mounted warriors, an effective corps for an offensive attack the next day.

Khalid formulated a simple but bold plan of attack. With his massed cavalry force he now intended to drive the Byzantine cavalry entirely off the battlefield so that the infantry, which formed the bulk of the Imperial army, would be left without cavalry support and thus be exposed and helpless when attacked from flank and rear. At the same time he planned to push a determined attack to turn the left flank of the Byzantine army and push them toward the ravine to the west.

Day 6:
Now, Khalid put his battle plan into action.

While the Muslim centre and left wing engaged the Byzantine armies on their fronts to pin them down, [42], Khalid deployed his cavalry and charged the Byzantine left flank. At the same time he also dispatched a mounted regiment to engage and pin down the Byzantine cavalry of the left wing. And also at the same time Amr attacked from the front, taking his right flank of the Muslim army and pressing against the left flank of the Imperial army.

The left wing of the Byzantines, consisting mainly of Slavs under Qanateer, resisted against this double sided attack but, getting no support from their own cavalry which was busy dealing with the cavalry charge against them, fell back into the left half of the centre - onto the Armenians of Mahan. As the Byzantine left wing retreated, Amr, with his corps on the Muslim right wing, drove home his advantage and wheeled into an attack on the Byzantine left half of the center from their left flank. The Byzantine left centre was already in imbalance due to the retreating Slav corps. At the same time Sharhabeel bin Hassana now pressed his attack against them from the front.

The left flank of the Byzantine army had now been turned and the Muslim infantry were pressing their advantage. So Khalid now detached his cavalry from this main fight and took them to join the dispatched regiment where the Byzantine cavalry of the left wing was driven off the battlefield to the north.

While this action was taking place on his left, Mahan now planned to respond by trying to concentrate all his cavalry regiments behind the center to counterattack the advancing massed Muslim cavalry.

But he was not quick enough, and before Mahan could organise his disparate cavalry squadrons, Khalid had galloped his cavalry back to attack the concentrating Byzantine horse, falling upon them from the front and the flank while they were still maneouvering into formation. Muslim lightly armed horsemen were superb for these fluid situations, as they were able to attack, disengage, maneouver and strike again. Disorganised and disoriented, the Byzantine cavalry soon broke contact and dispersed to the north, leaving the infantry to it?s fate. This also included the mounted corps of Jabla who now scattered towards Damascus

As the Byzantine cavalry retreated in disorder, Khalid now turned his attentions to the main body of the Imperial army - the Armenian army of Mahan - attacking them from the rear. The Armenians were strong fighters who had come closest to defeating the Muslim army when they broke through two days earlier, but under a three pronged attack of Khalid's cavalry from the rear, Amr?s infantry from the left and Shurhabeel?s infantry from the front, and with no support, and with their ranks already disturbed by the retreating Slavs of Qanateer, they had no chance. The Armenian line broke and they fell back.

As the Armenians retreated, the entire Byzantine army was now in full retreat. Parts scattered in panic and parts fell back in good order west towards Wadi-ur-Riqqad.[43].

Khalid now turned this retreat into a rout, taking his cavalry towards the northwest so that no troops could escape from there, though before he could seal off all the gaps, a few thousand Byzantine troops escaped towards Damascus. The rest simply headed towards the ford which was the only safe crossing from the ravine of Waddi-ur-Riqqad.

But as the retreating Byzantine troops reached the ford they were met with the sight of a Muslim cavalry regiment under Zirrar ibn al-Azwar blocking their way at the ford. As part of his battle plan, Khalid had the night before sent 500 mounted troops towards that 500 meter wide ford to block the passage. In fact this was the route Khalid ibn Walid wanted the Byzantines to retreat along.

Now the advancing Muslim infantry caught up from the east and the cavalry under Khalid?s command reached from the north to link up with the regiment which was blocking the passage from the west. To the south lies the deep ravine of Yarmouk River, to where Byzantine troops had been corralled and were now starting to become surrounded.[3]

The final phase of the battle began as the exhausted Byzantine corps were pushed back towards the ravine from the front, while from the flanking side they were pushed towards the center so that imbalance could be created in the army. By this time the Imperial army had lost all formation and cohesion. They had reached that point which all commanders fear the most: when their troops become an armed rabble. In fact the Byzantine troops were pushed together so tightly that they were unable to use their weapons freely and soon they broke, attempting to find a way through the ravine, unsuccessfully. Some of the Byzantines fell into the ravine whilst the others fell fighting or were captured, effectively ending the battle.

Immediately after this operation was over Khalid ibn al-Walid with his mobile guard moved north to pursue the retreating Byzantine soldiers, he found them near Damascus and attacked. In the ensuing fight the Commander in Chief of the Imperial army, the Armenian king Mahan who had escaped the fate of most of his men at Yarmouk, was killed. Khalid then entered Damascus where he was welcomed by the local residents, thus recapturing the city.[3] When news of the disaster reached the Byzantine Emperor Heraclius at Antioch, it is said that he bade a last farewell to Syria, saying,

? "Farewell Syria, my fair province. Thou art an enemy's now" ?

Heraclius then left Antioch for Constantinople. Abandoning Syria, the Byzantine Emperor began to concentrate his remaining forces on a defense of Egypt instead. There the Byzantines were destined to meet Amr ibn al-A'as again, he who had commanded the right flank of Khalid's army at Yarmouk.

The Battle of Yarmouk is one of those rare brilliant examples in military history where an inferior force manages by guile, courage and intelligence, to overcome a superior one. In this respect it was tactially as significant as the Battle of Austerlitz some twelve centuries later.

But this was the battle that Mahan King of Armenia lost, as much as the battle that Khalid ibn al-Walid won. The Imperial Byzantine commanders allowed their enemy to have the battlefield of his choosing. But even then there was no critical tactical point against them. Khalid knew all along that he was up against a force superior in number and arms and until the last day of the battle he had conducted an essentially defensive campaign suited to his relatively limited resources. But when he decided to take the offensive and attack on the final day of battle, he did so with a sense of imagination, foresight and courage that none of the Byzantine commanders ever displayed. Although he commanded a numerically inferior force and needed all the men he could muster, he nevertheless had the confidence and foresight to dispatch a cavalry regiment the night before his assault to seal off a critical path of retreat for the enemy army. Khalid ibn al-Walid was one of the finest cavalry commanders in history and his use of mounted warriors throughout the battle showed just how well he understood the potentials and strengths of mounted troops. His mobile guard moved quickly from one point to another, always turning the course of events wherever they appeared, and then just as quickly galloping away to turn the course of events elsewhere on the field.

Mahan and his Byzantine commanders never dealt with this mounted force effectively. Their own Byzantine cavalry never played a significant role in the battle and were held in static reserve for most of the six days. They never pushed their attacks and even when they obtained what could have been a decisive breakthrough on the fourth day, they were unable to exploit it. There appeared to be a decided lack of resolve among the Imperial command. The original strategy by Heraclius, to destroy the Muslim troops in Syria piecemeal, needed rapid and quick deployment to be implemented, but the commanders on the ground never displayed these qualities. Ironically, on the field at Yarmouk, Khalid carried out on a small tactical scale what Heraclius had planned on a grand strategic scale: by rapidly deploying and manoeuvering his mobile guard, Khalid was able to temporarily concentrate sufficient forces at specific locations on the field to defeat the Byzantine troops in detail. While Mahan, moving parts of his army largely in isolation from each other, was never able to make his numerical superiority count. At no point did Mahan attempt to concentrate a superior force to achieve a critical breakthrough. Although he was supposedly on the offensive 5 days out of the six, his battle line remained remarkably static. This all stands in stark contrast to the very successful offensive plan that Khalid carried out on the final day; when he re-organised virtually all his cavalry and committed them to a grand maneouvre that won the battle.