The Battle of Yarmouk River (or Yarmuk River; also written as the Battle of Jabiya-

Yarmuk) was fought over the course of six days, from 15 to 20 August 636 CE,
between the Muslim army of the Rashidun Caliphate (632-661 CE), under Khalid ibn
al-Walid (d. 642 CE) and the Byzantine legions, under field commander Vahan of
Armenia (d. 636 CE). Fighting took place near the Yarmouk River in the Jordan
valley, and the battle was a decisive victory for the heavily outnumbered Rashidun
army. This victory permanently shifted the dominion in the Levant and Syria from
the Byzantine Empire to the Caliphate. Moreover, this was the magnum opus of
Khalid, who has been immortalized in legends for his triumph.

Illustration of the battle of Yarmouk (636 CE)

Illustration of the battle of Yarmouk (636 CE)
Unknown (Public Domain)
Prelude
After the death of the Islamic Prophet Muhammad in 632 CE, his closest confidant,
Abu Bakr (r. 632-634 CE) assumed control over the community as the first Caliph of
the Rashidun Caliphate (632-661 CE). Having taken the scepter, Abu Bakr faced an
open rebellion from all corners of Arabia. Various tribes, who had bowed before the
Prophet, declared that their covenant with Muhammad had ended with his life. These
renegades were labeled as apostates and were confronted with the full might of
Rashidun military in a series of engagements, later styled as the Ridda Wars (632-
633 CE).

Khalid had distinguished himself in warfare, earned the nickname of Saif Allah, &
was one of the best strategists of his time.
The most notable Rashidun military leader in this conflict was Khalid ibn al-Walid
(l. 585-642 CE), a man cherished by Abu Bakr, despite his flaws, for his
unparalleled talent in warfare. He had distinguished himself in warfare, earned the
nickname of Saif Allah (the sword of God), and was easily one of the best
strategists of his time. He proved to be instrumental in ensuring Rashidun victory
against the rebels, all of whom were subdued within a year.

Abu Bakr then launched the expansion of his empire into Iraq and Syria. Khalid's
division was sent to the former, where the caliphal army enjoyed much success under
him, but the threat of a Byzantine counterattack on the Syrian divisions, who had
gained considerable ground, prompted Abu Bakr to send Khalid there. Khalid crossed
the barren and trackless desert with his best men, using camels as water
reservoirs, and emerged on the fringes of Syria, where after some raiding and
conquest, he confronted and defeated a major Byzantine force at Ajnadayn (634 CE).

Abu Bakr, in the meanwhile, died of natural causes and was replaced by Umar (r.
634-644 CE), who stripped Khalid of his command, either because of a personal
grudge or because of his harsh personality. In his stead, Abu Ubaidah (l. 583-639
CE), a man renowned for his moral standards, was made the governor of Syria and the
commander of the Rashidun corps stationed there. The Muslims continued to engulf
the area, Damascus fell in 634 CE, the Byzantine garrison of Palestine was defeated
in the battle of Fahl (Pella; 635 CE), and Emesa (Homs) fell in 636 CE, leaving
Aleppo only a march away. The Byzantine emperor Heraclius (r. 610-641 CE),
determined to rid his land of the Arabs, mustered up a huge force at Antioch to
crush the invaders.

Khalid ibn a-Walid's Invasion of Syria

Khalid ibn a-Walid's Invasion of Syria
Mohammad adil (GNU FDL)
Belligerents
Although Arab chroniclers are notorious for inflating enemy numbers and shrinking
their own in comparison, the Muslim army was indeed heavily outnumbered by the
Byzantines on this occasion. A huge imperial force, consisting of Greeks, Slavs,
Franks, Armenians, Georgians, and Ghassanid (Christian) Arab vassals of Syria, had
a cumulative strength of around 40,000.

The Byzantine field commander, Vahan, was an Armenian and had formerly served as
the Magister militum per Orientem (Master of the Soldiers in the East; top military
commander) of Emesa. Theodore Trithurius, the state treasurer, held the command in
theory, but his presence was merely to boost the morale of the troops. Another
notable figure among the Byzantine ranks was Jabalah (d. 645 CE), the Ghassanid
ruler who had profited much from his alliance with the Byzantines and felt no
compunction in serving them against fellow Arabs.

The Rashidun army, originally spread across Palestine, Jordan, Caesarea, and Emesa
after their earlier triumphs, was regrouped and withdrawn southwards to the Yarmouk
Plateau. There, they were further reinforced by fresh combatants from Medina, the
Islamic capital, bringing their numbers up to 20-25,000 on the eve of the battle.

The Battle
Although Khalid was not officially in command, he was highly respected for his
skill in battle, and Abu Ubaidah, who lacked such expertise, ceded the command to
him. Initially, the Byzantines delayed their advance, wishing to strike
simultaneously with the Sassanids whom they had allied with after decades of war.
But the ruler of the Sassanian Empire, Yazdegerd III (r. 632-651 CE), required time
to prepare, and the Byzantines, ever-impatient to drive the Arabs out, advanced on
their own. Khalid, knowing that their position in the north was vulnerable,
withdrew his forces all the way to the valley beyond the Yarmouk River. This
plateau was an undulating flat land-mass, making it very suitable for the Arab
light cavalry, which accounted for a quarter of his army's strength.

Calligraphy of Khalid ibn al-Walid's name

Calligraphy of Khalid ibn al-Walid's name
UsmanKhanShah (CC BY-SA)
Negotiations dragged on for around three months, and during this time, the Rashidun
army was reinforced from Medina. Not content with further delay, both sides
prepared for combat. Vahan used his numerical superiority to fan out his frontline
to about 13 kilometers, forcing the Muslim line to stretch thinner and cover a
ground of 12 kilometers to face them. The Byzantine forces were placed in front of
the Allan river, with their right anchoring the gorge to the south and their left
bordering the Jabiya hills. Vahan arranged his forces as such:
Ghassanid light cavalry, under Jabalah, acted as the vanguard for screening and
skirmishing
The left flank consisted of the Slavic infantry (facing the Muslim right)
Armenian infantry (under Vahan himself) and European contingents made up the center
Greek infantry manned the right flank (facing the Muslim left)
Cavalry divisions, mostly consisting of cataphracts - elite heavy mounted troops,
were stationed behind each flank and the two central divisions
Khalid arrayed his 36 infantry regiments in a similar fashion, in front of the
Harir River, with 3 light cavalry divisions positioned behind the line, and one
larger cavalry reserve under his personal command in the rear. Unlike the
multiethnic Byzantine forces, the Arabs were united not only in their nationalist
sentiment but also by a common faith. In both armies, infantry consisted of melee
fighters and skirmishers (such as archers), and although the Muslims lacked heavy
troops, which abounded in the ranks of their foes, they made up for this loss with
higher mobility and unparalleled skill in hand-to-hand combat.

Troop Arrangement at the Battle of Yarmouk

Troop Arrangement at the Battle of Yarmouk
Mohammad Adil (CC BY-SA)
On 15 August, fighting was initiated with several duels, as was the custom in the
region, in which the Muslim champions appear to have bested their foes. Following
this, Vahan ordered the advance of merely a third of his force to probe the Muslim
lines for weaknesses; the fighting was not extreme and the Byzantines retreated
after the day's end. Seeking to catch the Arabs by surprise, Vahan advanced at dawn
on the following day, probably knowing that the Muslims would be busy offering
their (Fajr) prayers. Khalid, however, had stationed scout patrols ahead of the
main army in anticipation of such a surprise attack. The Byzantines, upon finding
the Muslims completely alert, attacked anyway and locked their center in place as
their flanks delivered the blows from either side. Muslim flanks, first the right
and then the left, retreated to their camps, where, aided by their women, they
managed to hold the enemy until relieved by Khalid's cavalry reserve. The resolve
of the dauntless Muslim women has been eloquently narrated by historian David
Nicolle:
…the Muslim right fell back and Byzantine troops reached one or more of the Arab
camps. There the retreating Muslim infantry and cavalry were met by their womenfolk
who abused them for running away, beat drums, threw stones, and sang songs to shame
the men back into battle. The same scenario was enacted slightly later on the
Muslims' left flank... (68)

The Byzantines continued to attempt to push through the Muslim ranks for the next
two days, and just as Vahan's troops appeared to have made a breakthrough, Khalid
would use his reserve to send them on the run. Seeking to buy some respite for his
men, the Armenian field commander sued for peace on the fifth day. To the great
shock of Abu Ubaidah, who was happily willing to comply, Khalid rejected the offer;
the cunning general knew that the time to act was then. The fifth day ended without
much fighting, and Khalid, knowing that his foes were demoralized, prepared an all-
out assault for the next day, which had been his plan all along.

Yarmouk Valley
Yarmouk Valley
Mohammad Adil (CC BY-SA)
In the dark of the night, he sent a cavalry detachment around the field to take
over the only bridge on the Wadi Ruqqad, cutting off the only escape route of the
imperial army. The fighting started on 20 August 636 CE with another duel, where
Abu Ubaidah got the best of his foe, a Greek commanding officer named Gregory, and
then the entire Muslim line charged. As the infantry locked their kind on the
opposing side in place, Khalid sprang into action and led a huge cavalry force,
gathered from all of his cavalry divisions, around the Byzantine left flank. Vahan,
realizing too late that he had been outwitted, failed to organize his disarrayed
cavalry in time, and the Muslims smashed the Byzantine left into their center.
Surrounded on three fronts, and with no hope of assistance from the cataphracts,
the imperial troops began to rout, but unbeknownst to them, their escape had
already been cut off. Imperial troops were massacred in their retreat, and many
drowned in the river, while some fell to their deaths from steep hills of the
valley (many jumped to their deaths to avoid a melee with the Arabs). Khalid all
but annihilated his foe and secured a crushing victory, whilst only taking around
4,000 casualties. Vahan either perished in the battle or, according to some,
adopted a monastic lifestyle after the pulverizing defeat. Jabalah is said to have
defected to the Rashidun side during the climax of the battle, and accepted Islam
in 638 CE, only to apostatize later on and escape to Armenia.

Aftermath & Conclusion

With this stunning victory, the Muslims held uncontested power over the Levant and
Syria. Jerusalem, a holy city for three monotheistic religions - Judaism,
Christianity, and Islam - surrendered personally to the Caliph in 637 CE after
receiving assurances of safety. Khalid ibn al-Walid, however, did not receive the
prestige that was rightfully his. Umar officially discharged him of duty upon his
visit to the region soon after the battle. Though Khalid's morals did not equal
Umar's standards (there were some controversies against him), this action was much
criticized, for it had been Khalid who saved the Muslim cause from certain doom,
but Umar announced that he had done so to show the people that it was God alone who
gave them victory.

Khalid retired peacefully (although he is said to have complained to Umar, saying

that he was being treated like dirt), died in 642 CE, and was buried in Homs.
Though he had been encouraged by many to rebel against Umar, Khalid refused to do
so. The Muslims soon engulfed Egypt, parts of North Africa, and several islands in
the Mediterranean. On the Sassanian front, a similarly spectacular victory at the
Battle of al-Qadisiyya (636 CE) also opened up a similar channel of conquest,
swelling the Islamic empire to a titanic size in a matter of mere decades.

Khalid ibn al-Walid Mosque, Homs

Khalid ibn al-Walid Mosque, Homs
Travpacker.com (CC BY-ND)
Muslim success against these superpowers was due to a combination of reasons.
Firstly, their maltreatment of the Syrian and Iraqis, respectively, inclined these
people to not only welcome the new invaders but even assist them. Secondly, the
years of fighting with each other had significantly weakened the two colossal
empires. Thirdly, though the equipment of the Arabs did not parallel that of their
foes, their skill in combat was unexcelled and the contributions of great generals
like Khalid ibn al-Walid cannot be underestimated either.