Expansions during Abu Bakr's reign

Arab Muslims first attacked Sassanid territory in 633, when Khalid ibn al-Walid invaded Mesopotamia (then known as the Sassanid province of Asōristān; roughly corresponding to modern-day Iraq), which was the political and economic centre of the Sassanid state.^[13]

Expansions during Umar's reign

Abu Bakr was aware of Umar's power and ability to succeed him. His was perhaps one of the smoothest transitions of power from one authority to another in the Muslim lands.^[14] Before his death, Abu Bakr called Uthman to write his will in which he declared Umar his successor. In his will he instructed Umar to continue the conquests on the Iraqi and Syrian fronts.

Following the transfer of Khalid to the Byzantine front in the Levant, the Muslims eventually lost their holdings to Sassanid counterattacks. The second Muslim invasion began in 636, under Sa'd ibn Abi Waqqas, when a key victory at the Battle of al-Qadisiyyah led to the permanent end of Sassanid control west of modern-day Iran. For the next six years, the Zagros Mountains, a natural barrier, marked the border between the Rashidun Caliphate and the Sassanid Empire. In 642, Umar ordered a full-scale invasion of Persia by the Rashidun army, which led to the complete conquest of the Sassanid Empire by 651. Directing from Medina, a few thousand kilometres away, Umar's quick conquest of Persia in a series of well-coordinated, multi-pronged attacks became his greatest triumph, contributing to his reputation as a great military and political strategist.

The military conquests were partially terminated between 638 and 639 during the years of great famine in Arabia and plague in the Levant. During his reign the Levant, Egypt, Cyrenaica, Tripolitania, Fezzan, eastern Anatolia, almost the whole of the Sassanid Persian Empire including Bactria, Persia, Azerbaijan, Armenia, Caucasus and Makran were annexed to the Rashidun Caliphate. Prior to his death in 644, Umar had ceased all military expeditions apparently to consolidate his rule in recently conquered Roman Egypt and the newly conquered Sassanid Empire (642–644). At his death in November 644, his rule extended from present day Libya in the west to the Indus river in the east and the Oxus river in the north.^[15]

Historians estimate more than 4,050 cities were conquered during the reign of Umar.^[15]

Expansions during Uthman's reign

In 644, prior to the complete annexation of Persia by the Arab Muslims, Umar was assassinated by Abu Lu'lu'a Firuz, a Persian craftsman who was captured in battle and brought to Arabia as a slave.

Uthman ibn Affan, the third caliph, was chosen by a committee in Medina, in northwestern Arabia, inAH 23 (643/644). The second caliph, Umar ibn al-Khattab, was stabbed by Abu Lu'lu'a Firuz, a Persian slave.^[16] On his deathbed, Umar tasked a committee of six with choosing the next caliph among themselves.^[17] These six men from the Quraysh, all early companions of the Islamic prophet Muhammad, were

• Ali ibn Abi Talib
• Abd al-Rahman ibn Awf
• Sa'd ibn Abi Waqqas
• Uthman ibn Affan
• Zubayr ibn al-Awwam
• Talhah ibn Ubaydullah

Where they unanimously selected Uthman as the successor. During his rule, Uthman's military style was less centralised as he delegated much military authority to his trusted kinsmen—e.g., Abdullah ibn Aamir, Muawiyah I and Abdullāh ibn Sa'ad ibn Abī as-Sarâḥ—unlike Umar's more centralized policy. Consequently, this more independent policy allowed more expansion until Sindh, in modern Pakistan, which had not been touched during the tenure of Umar.^[18]

Muawiyah I had been appointed the governor of Syria by Umar in 639 to stop Byzantine harassment from the sea during the Arab-Byzantine Wars. He succeeded his elder brother Yazid ibn Abi Sufyan, who died in a plague, along with Abu Ubaidah ibn al-Jarrah. Now under Uthman's rule in 649, Muawiyah was allowed to establish a navy, manned by Monophysitic Christians, Copts, and Jacobite Syrian Christian sailors and Muslim troops, which defeated the Byzantine navy at the Battle of the Masts in 655, opening up the Mediterranean.^{[19][20][21][22][23]}

In Hijri year 31 (c. 651), Uthman sent Abdullah ibn Zubayr and Abdullah ibn Saad to reconquer the Maghreb, where he met the army of Gregory the Patrician, Exarch of Africa and relative of Heraclius, which is recorded to have numbered between 120,000 or 200,000 soldiers.^[24] The opposing forces clashed at Sabuthilag (or Sufetula), which became the name of this battle. Records from al-Bidayah wal Nihayah state that Abdullah's troops were completely surrounded by Gregory's army. However, Abdullah ibn Zubayr spotted Gregory in his chariot and asked Abdullah ibn Sa'd to lead a small detachment to intercept him. The interception was successful, and Gregory was slain by Zubayr's ambush party. Consequently, the morale of Byzantine army crumbled and soon they were routed.^[24]

Some Muslim sources claim that after the conquest of northern Africa was completed by Muhammad ibn Jarir al-Tabari,^[25] Abdullah ibn Sa'd continued to Spain. Spain had first been invaded some sixty years earlier during the caliphate of Uthman. Other prominent Muslim historians, like Ibn Kathir,^[26] have quoted the same narration. In the description of this campaign, two of Abdullah ibn Saad's generals, Abdullah ibn Nafiah ibn Husain, and Abdullah ibn Nafi' ibn Abdul Qais, were ordered to invade the coastal areas of Spain by sea, aided by a Berber force. They succeeded in conquering the coastal areas of Al-Andalus. It is not known where the Muslim force landed, what resistance they met, and what parts of Spain they actually conquered. However, it is clear that the Muslims did conquer some portions of Spain during the caliphate of Uthman, presumably establishing colonies on its coast. On this occasion, Uthman is reported to have addressed a letter to the invading force:

Constantinople will be conquered from the side of Al-Andalus. Thus, if you conquer it, you will have the honor of taking the first step towards the conquest of Constantinople. You will have your reward in this behalf both in this world and the next.

Although raids by Berbers and Muslims were conducted against the Visigothic Kingdom in Spain during the late 7th century, there is no evidence that Spain was invaded nor that parts of it were conquered or settled by Muslims prior to the 711 campaign by Tariq.

Abdullah ibn Saad also achieved success in the Caliphate's first decisive naval battle against the Byzantine Empire, the Battle of the Masts.^[27]

Rashidun Caliphate at its peak under Uthman (654)

To the east, Ahnaf ibn Qais, chief of Banu Tamim and a veteran commander who conquered Shustar earlier, launched a series of further military expansions by further mauling Yazdegerd III near the Oxus River in Turkmenistan^[28][29] and later crushing a military coalition of Sassanid loyalists and the Hephthalite Empire in the Siege of Herat.^[28] Later, the governor of Basra, Abdullah ibn Aamir also led a number of successful campaigns, ranging from the suppression of revolts in Fars, Kerman, Sistan, and Khorasan, to the opening of new fronts for conquest in Transoxiana and Afghanistan.^[30]

In the next year, 652 AD, Futh Al-Buldan of Baladhuri writes that Balochistan was re-conquered during the campaign against the revolt in Kermān, under the command of Majasha ibn Mas'ud. It was the first time that western Balochistan had come directly under the laws of the Caliphate and it paid an agricultural tribute.^[31][32]

The military campaigns under Uthman's rule were generally successful. Regarding the fate of their adversaries, unlike the Sasanian Persians, the Byzantines, after losing Syria, retreated back to Anatolia. As a result, they also lost Egypt to the invading Rashidun army, although the civil wars among the Muslims halted the war of conquest for many years, and this gave time for the Byzantine Empire to recover.

Infantry horses and camels

Aside from Donner's report that each caliphate's soldiers possessed camels,^[57] Dr Lee Eysturlid noted the Diwan al Jund around 640 AD has recorded that each caliphate's soldiers already possessed horses.^[58] The camels mainly supplied from Al-Rabadha and Diriyah.^[59][60]

Armour

Reconstructing the military equipment of early Muslim armies is problematic relative to contemporary neighbouring armies such as Byzantium's as the visual representation of the early caliphate armaments was very limited physical material and difficult to date.^[61] However, Nicolle theorized the Muslim army used hardened leather scale or lamellar armour produced in Yemen, Iraq and along the Persian Gulf coast. Mail armour was preferred and became more common later during the conquest of neighbouring empires, often being captured as part of the booty. It was known as Dir, and was opened part-way down the chest. To avoid rusting it was polished and stored in a mixture of dust and oil.^[62]

Mail shirts were recorded already used by the Arabs before the advent of Islam.^[63] During the Battle of Uhud, Jami'at Tirmidhi recorded Zubayr ibn al-Awwam testimony that prophet Muhammad wearing two layers of mail coat.^[64][65] However, there is still not yet archaeological founding of Arabic armor in such time.^[63] David Nicolle are certain the prevalence of leather armour among Arabs since the pre-Islamic era, due to the fact that the leather was one of important commodities which made the Meccan traders rich, which correlated with the war between the Byzantine and Sassanian Empires during 6th century as there was increased demand for such military goods that Nicolle called “military leatherwork".^[66]

Helmets

Muslim headgear included gilded helmets—both pointed and rounded—similar to that of the silver helmets of the Sassanid Empire. The rounded helmet, referred to as "Baidah" ("Egg"), was a standard early Byzantine type composed of two pieces. The pointed helmet was a segmented Central Asian type known as "Tarikah". Mail armour was commonly used to protect the face and neck, either as an aventail from the helmet or as a mail coif the way it had been used by Romano-Byzantine armies since the 5th century. The face was often half covered with the tail of a turban that also served as protection against the strong desert winds.

Another type of helmet used by the Rashidun army were the Mighfars.^[67]

Swords

Sayf was a broad sword with a peculiar hooked pomel used by the Rashidun army.^[68] Early Arab chroniclers mentioned two types of swords:

• Saif Anith, which was made of iron
• Saif Fulath or Muzakka, which was made of steel material.^[68]

These broad swords came to Arabia through Yemen port during the pre-Islamic ʿĀd and Jurhum era^{[Notes 3]}. These Indian-made swords were forged from wootz steel.^[69] Aside from Yemen, high-quality Indian swords also introduced to pre-Islamic Arab through port of Ubulla, Persian Gulf.^[70] The Arabs in Medina during the time of Muhammad were able to manufacture Sayf swords independently.^[69] There are records that some nobles made their sword with silver materials, such as prophet Muhammad sword and Zubayr ibn al-Awwam sword used which reported by from Anas ibn Malik and Hisham are made of silver or contain inscription of silver material.^[71][72] However, there is no archeological trace that such sword found yet.^[71]

Curved saber or Shamshir also existed during the early years of the caliphate.^[73] This type of saber allegedly belonged to the prophet Muhammad and is now in the Topkapi Museum.^[73] David Nicolle theorized that this type of saber is probably of central Asian, Avar or Magyar origin. Nicolle theorized it reached the early Muslim Arabs through the contact with Byzantium before the 6th century.^[73]

Shields

Large wooden or wickerwork shields were in use, but most shields were made of leather. For this purpose, the hides of camels and cows were used and it would be anointed, a practice since ancient Hebrew times. During the invasion of the Levant, Byzantine soldiers extensively used elephant-hide shields, which were probably captured and used by the Rashidun army.

Spears

Long spears which were used by infantry were locally made with the reeds of the Persian Gulf coast. The reeds were similar to that of bamboo.^[74] These Arab blacksmiths manufactured infantry spears called al-Ramh.^[75] There are two types of this spear:

• Arab blacksmiths used sharpened animal horns for the tip of the blade
• Usual iron which was sharpened and hammered first until it forms the blade.^[75]

During the Battle of Badr, the Prophet commanded his companions to use spears for middle-range combat. The raw material for making spears was available in Arabia.^[75]

Maces

The early caliphate army also used blunt weapon such as Mace, which named al-Dabbus.^[76] A round-headed, Persian style mace^[77]

Javelins

Wahshi ibn Harb, was a renowned javelineer who fought for pagan Quraish during the battle of Uhud and killed Hamza ibn Abdul-Muttalib with a javelin.^[78] After his conversion to Islam, he fought for the caliphate during the Battle of Yamama and personally killed apostate leader Musaylimah with a javelin throw.^[78]

Bows

Bow of Sa'd ibn abi-Waqqas at Medina railway museum

According to an ancient arabic manuscript of archery, Bows used by people of Arabs were locally made in various parts of Arabia; the most typical were the Hijazi bows. There are three types of Hijazi bows:

• Qadib variant is basically made from single stave of wood
• Masnu'ah variant are composite bows designed from a stave or two staves divided lengthwise with four composite materials of wood, horn, glue, and sinew
• Mu'aqabbah variant are bows designed with horn of goats placed in the belly of the bow and sinew placed on the back of the bow.^[85]

Arabs were able to master the art of Bowery and use it so effectively to even matched the qualities of Byzantines and Persians made. The most famous place for manufacturing bows was Za s r in al-Sham. which became the name renowned Zed bows (al-Kanä t in al-Zas riyyah). The Muslims continued to improve the manufacturing of bows and were able at one point to manufacture sophisticated machines (al Ma'arrah, a large crossbow).^[76] According to Latham in his work, Saracen archery, Muslim archers of early era has two types of arrows. The first were shorter darts called Nabl and Nushshab, which were shot using either a crossbow or a bow equipped with arrow guide, while the second type were longer arrows which were shot with standard handbows.^[86] The maximum useful range of the traditional Arabian bow was about 150 meters.

Horse

A purebred Arabian stallion, showing dished profile, arched neck, level croup and high-carried tail

Caliphate Arabian noble cavalry^{[Notes 5]} mostly rode the legendary purebred Arabian horse, by fact the quality breeding of horses were held so dearly by the early caliphates who integrated traditions of Islam with their military practice.^[94][95][96] The phenomenal speed, stamina, animal cognition, along with very well documented pedigrees quality even for modern era standard,^[97][98] caused the Rashidun leaders to initiate a formal programs to distinguish them from inferior hybrids with unknown pedigrees including horses recently captured from the defeated Byzantines and Persians.^[99] Long withstanding periods of Arabian nomadic society closeness with the horses also contributed to fertility of equestrian masters which produced best class horse breed in Arabia.^[100] This breed are known as a hot-blooded breed that are known for their competitiveness. Mounts quality was monitored carefully since the beginning of the caliphate. Ibn Hisham recorded in his chronicle the earliest mention of such effort were after the Siege series of Khaybar fotresses the Muslims acquired massive booties of horses. In response prophet Muhammad personally instructed the separation between purebred Arabian and the hybrid-class steeds.^[101]

This was practiced on a larger scale during the reign of caliph Umar. The caliph instructed Salman Ibn Rabi'ah al-Bahili to establish systematic military program to maintain the quality of caliphate mounts. Salman enlisted most of the steeds within realm of caliphate to undergo such steps:

1. Recording number and quality of horses available
2. Differences between the Arabian purebreed and the hybrid breeds was to be carefully noted.
3. Arabic structural Medical examination and Hippiatrica on each horses in regular basis including isolation and quarantine of sick horses
4. Regular training between horses and their masters to achieve the disciplined communication between them
5. Collective response training of the horses done in general routine
6. Individual response training of the horses on advanced level
7. Endurance and temperament training to perform in crowded and noisy place.^[101]

At the end of the program, both riders and horses obligated to enlisted in formal competition sponsored by Diwan al-Jund which consisted into two category:

1. Racing competition to measure the speed and stamina of each hybrids
2. Acrobat competition to measure the ability of the horses for difficult maneuvers during war.^[99]

Additionally, the already established cavalry divisions were obliged to undertook simulated combat operation raids during the winter and summer seasons, known as Tadrib al-Shawati wa al-Sawd'if, which were intended to maintain the quality of each cavalry forces, while also maintain the pressures towards the Byzantines, Persians, and other caliphate enemies while there is no major military campaign.^[99]

This profound tradition of breeding exaltation even became a basis for scholars of later era such as by Shafi'i jurist, Al-Mawardi, to establish the ruling of regular military share that the owner of noble purebreed Arabian (al‑khayl al‑ʿitāq) should be rewarded a share of booty three times of regular infantry soldiers, while owners of inferior mixed breeds received only twice infantry soldiers' share.^[94]

Equipment

Arabian caliphate cavalry wearing heavy armors as according to Eduard Alofs, contrary to the popular beliefs, the Arabian, both the Rashidun cavalry or the cavalry of Ghassanid and the Lakhmid kingdom were not lightly armored scout horsemen. In fact, classic chroniclers such as Tabari, Procopius, and the Manual of Strategikon implied that the Arabian cavalry during the 5th century onwards were well armored heavy mounted troopers, Arabians usually covered their armors with dull-colored coats to prevent the sunburn on their metallic armor caused by hot climate of desert climate.^[103] Such Arabian knights were named Mujaffafa by early historians, which according to Martin Hinds were technically "Arabian Cataphracts" as they are fully armored both riders and horses".^[104]

The early caliphate armies generally neglected the use of stirrups despite long knowing of stirrups. al-Jahiz commented that the Arabs spurned double iron stirrups as it is viewed as a weakness, while also provided hindrance for skillful riders to maneuver during battles and can be a disadvantage if the rider falls but his legs are stuck in the stirrups.^[105]

Caliphate horsemen used the following weapons in battle:

• Mounted archery with flying gallop was practiced by the early caliphate regular Arab cavalry from Rashidun era onwards.^{[99][106][103]} Alof theorized "Mubarizun" elite division also used archery in close-combat duels for maximum arrow penetration against opponent armor.^[107]
• Caliphate horsemen also used thrown javelins as their weapon. Zubayr ibn al-Awwam, a seasoned Muhajir and early convert, who almost always brought horses during battle,^[108] is recorded to have killed his opponents at least in two occasions during his life. He killed Quraish nobleman Ubaydah ibn Sa'id from Umayyad clan during the Battle of Badr, who was wearing a full set of armor and Aventail that protected his entire body and face. Zubayr hurled his javelin aiming at the unprotected eye of Ubaydah and killed him immediately.^[87] The second occasion is during the Battle of Khaybar, Zubayr fought in a duel against a Jewish nobleman Yassir which Zubayr killed with a powerful javelin strike.^[87] Firsthand witnesses reported that Zubayr brandishing himself across the battlefield during the Battle of Hunayn while hung two javelins in his back.^[87]
• Early caliphate cavalry held their lance overhead posture with both hands.^[103]

Mubarizun

A select few apparatus of mounted soldiers who particularly skilled in duel using swords and various weapons were formed a commando unit called known as Mubarizuns.^[105]

Their main task was charging with their horses until they find the enemy generals or field officers, in order to kidnap or slay them in close combat, so the enemy will lose their commanding figure amidst of battle.^[109]

Historical reconstructors like Marcus Junkelmann has practiced in historical reenactment that mounted close combat specialists like Mubarizuns could fight effectively on top of their mounts even without stirrups.^[105] This is used by Alofs as an argument to debuff the majority historian beliefs that horsemen cannot fight effectively in close combat if they rode their horse without stirrups.^[105]

Aside from fighting with swords, lance, or mace, Mubarizuns also possessed a unique ability to use archery in close combat, where Alofs theorized that in mid range about five meters from the adversary, the duelists will exchange his lance with his bow and shoot the enemy from close range to achieve maximum penetration, while the duelist held the lance strapped between right leg and saddle.^[107]

Mahranite cavalry

Map of contemporary Yemen showing Al Mahrah Governorate from where Mahri tribes hailed.

Caliphate cavalry recruited from Al-Mahra tribe were known for their military prowess and skilled horsemen that often won battles with minimal or no casualties at all, which Amr ibn al As in his own words praised them as "peoples who kill without being killed"^{[Notes 6]}. Amr was amazed by these proud warriors for their ruthless fighting skill and efficiency During Muslim conquest where they spearheaded Muslim army during the Battle of Heliopolis, the Battle of Nikiou, and Siege Alexandria.^[110] Their commanders, Abd al-sallam ibn Habira al-Mahri were entrusted by 'Amr ibn al-'As to lead the entire Muslim army during the Arab conquest of north Africa. Abd al-sallam defeated the Byzantine imperial army in Libya, and throughout these campaigns Al-Mahra were awarded much land in Africa as recognition of their bravery.^[110] When Amr established the town of Fustat, he further rewarded Al-Mahri members additional land in Fustat which then became known as Khittat Mahra or the Mahra quarter.^[110] This land was used by the Al-Mahra tribes as a garrison.^[110]

During the turmoil of Second Fitna, more than 600 Mahranites were sent to North Africa to fight Byzantines and the Berber revolts.^[110]

Kharijite rebels

The 8th century chronicler Al-Jahiz noted the ferociousness of Kharijites horsemen, who spent parts of their early career in Kufa as Rashidun garrison troops during the Muslim conquest of Persia before their rebellion against the caliphate.^[74] Al-Jahiz pointed out Kharijites steeds' speed could not intercepted by most rival cavalrymen in the medieval era, save for the Turkish Mamluks.^[111] Notable seditionist warriors included Abd Allah ibn Wahb al-Rasibi from Bajila tribe, who participated in the early conquests of Persia under Sa'd ibn abi Waqqas.^[112]

Al-Jahiz also added that the Kharijites were feared for their cavalry charge with their lances which could break any defensive line, and almost never lose when pitted against an equal number of opponents.^[111] Dr. Adam Ali MA, PhD. postulated that Al-Jahiz assessment of the quality Kharijites quality are synonymous with the regular Arab cavalry as general in term of speed and charging maneuver.^[111] Their common ground with the caliphate military was even highlighted further by Professor Jeffrey Kenney, who traced back through older traditions that the embryo of Kharijites was even existed back in the times of prophet Muhammad, in the form of figure named Dhu'l Khuwaisira at-Tamim,^[113] one of Banu Tamim chieftain who appeared after the Battle of Hunayn who protested the war spoils distribution.^[114] In fact, ʿAbd al-Malik ibn Ḥabīb, a jurist and historian in the 9th century described the Berber Kharijites as a mirror match which resembles the Arabic caliphate martial tradition, except the loyalty to authority.^[115]

Ibn Nujaym al-Hanafi, Hanafi scholar said about Kharijites: "... kharijites are a folk possessing strength and zealotry, who revolt against the government due to a self-styled interpretation. They believe that government is upon falsehood, disbelief or disobedience that necessitates it being fought against, and they declare lawful the blood and wealth of the Muslims...”.^[116]

Catapults

Catapults, called Manjaniq, were evident in the history of the early caliphates. There is a long history of the Muslim armies from the battle of Khaybar. The prophet breached a Jewish fortress with catapults. Later on, Urwah ibn Masʽud and Ghaylan ibn Salamah also reportedly travelled to Jurash, near Abha in southwestern of Asir region in order to learn how to construct various Manjaniq catapults and Dabbabah siege ram as the city of Jurash were known for its siege workshops industry.^[117] Christides highlighted the high learning curves of the Arabs during the early caliphates that they could catch up with more established civilizations such as Byzantine in making complex war machines such as the Manjaniq catapult.^[118]

In the era of the caliphate, Catapults were used extensively in siege operations whenever the Muslim armies were expected to remain entrenched in one area for a long duration. Examples include Abu Ubaydah and Khalid's besieged Damascus, and furious artillery bombardments by Amr ibn al-As during the second siege of Alexandria which immediately caused the Christian garrison to surrender.^[119] Another record of such siege engines operations came from Abdallah ibn Sa'd's attack on the capital of Makuria, where the catapult engine of Abdallah caused the main cathedral structure of Makuria to crumble, compelling King Qalidurut to agree to ratify a ceasefire agreement with the former.^[120] The forces of Sa'd ibn Abi Waqqas were also reported to able to quickly construct at least twenty siege engines during the Second siege of Babylon, despite their relatively short stints in the area after the battle of Qadisiyyah.^[119] According to an obscure record from Sebeos, Mu'awiyah's fleet which was led by Bisr ibn abi Artha'ah is also reported to carry unspecified artillery engines that can throw "balls of Greek fire" within his ships during the siege of Constantinople.^[121]

Siege towers

Siege towers with scaling ladders are named al-Dabbdbah or al-dabr.^[46] These wooden towers moved on wheels and were several stories tall. They were driven up to the foot of the besieged fortification and then the walls were pierced with a battering ram. Archers guarded the ram and the soldiers who moved it.^[122]

Other engines

Regular Muslim infantries also qualified on the battlefield construction and engineering such as when they were able to perfect the art of building pontoon bridges which allowed them to gain the upper hand during the Battle of the Bridge.^[123] Their expertise on this field also helped during the last phase of the Siege of Damascus, when the Muslim army built water rafts and dinghies to cross the trench.^[123]

Al-Abna'

Al-Abnāʾ was the descendants of Sasanian officers and soldiers of Persian and Daylam origins who intermarried with local Yemeni Arabs after they taken over Yemen from the Aksumite in the Aksumite–Persian wars.^[124] The Abnas had been garrisoned in Sanaa and their surrounding Their leaders converted to Islam and were active in the early Muslim conquests. They were gradually absorbed into the local population.^[124] They are considered siege-warfare experts.^[111] However, al-Jahiz outlined al-Abna lacked medieval era standard mobility.^[111]

Notable figures hailed from al-Abna was Fayruz al-Daylami, hero of caliphate who defended Yemen for a decade during Apostate wars, and Wahb ibn Munabbih, a prolific Rāwī of Hadith who later became a judge during the rule of caliph Umar ibn Abd al-Aziz.

Greeks

Some Greeks joined the caliphate army after they defected from Byzantine army. One example is Joachim, garrison commander of Aleppo, who defected along with his 4,000 garrison troops and fought loyally under the caliphate later.^[88]

Persian Asawir

As the conquest of Persia progressed, some Sassanid gentry converted into Islam and joined the Rashidun; these "Asawira"

Al-Jahiz outlined the quality of these Persians, which he identified as Khurasaniyyah, as powerful heavy cavalry with considerable frontal charge power, although they lacked speed.^[111] Al-Jahiz also claims the downside of the Persians was if their charge failed to break the enemy, they tended to give up fighting and were easily routed.^[111]

They continued service under the caliphate until Abd al-Rahman ibn Muhammad ibn al-Ash'ath's rebellion. This heavily armored cavalry crushed by regular Arab cavalry led by Al-Hajjaj ibn Yusuf which possess more skill and discipline in Battle of Dayr al-Jamajim.^{[125][126][127][128][129]} As Hawting highlighted the different performance between caliphate cavalry and those of Abd al-Rahman al-Ash'ath's army including those of Persian Asawir, that "between the discipline and organisation of the Umayyads and their largely Syrian support and the lack of these qualities among their opponents in spite of, or perhaps rather because of, the more righteous and religious flavour of the opposition" is a recurring pattern in the civil wars of the period.^[127]

Jats

As the territory of caliphate has reached Sindh, there were reports that the local Jats had converted to Islam and even entered the military service.^[130] A notable local named Ziyad al-Hindi recorded has been entered the service under caliph Ali.^[131]

Arabic Christian levy

Chronicler Faraj recorded in his Fann 'Idarat al-Ma'arakah fi al-Islam that for certain situations, caliph Umar allowed a distinct unit which had not yet embraced Islam to be enlisted for military service. Prior to the Battle of Buwaib, Umar allowed al-Muthanna ibn Haritha to recruit Arab members of banu Taghlib and banu Nimr who had not yet embraced Islam for his service.^[132]

Camel defensive lines

According to John Walter Jandora in his Yarmouk reconstruction study, for the open-battle scenario, the abundance of camels brought by the army during their campaigns were used to form a line of camels positioned on the rear of Muslim battle lines, between the infantry lines and the camp perimeter which were positioned behind them,^[55] where reserve troops (al-Saqah), supplies and camp followers were located. Jandora argued it is used as a fail-safe, in case of breaches by enemy cavalry charges, which act as a deterrent that even stopped the powerful charge of the Byzantine Cataphract due to the beasts' large frames and foul tempers.^[55][142]

Mahranite camelier corps

Amr ibn al-As led a ruthless cavalry corps from tribes of Al-Mahra who were famous for their "invincible battle skills on top of their mounts", during the conquests of Egypt and north Africa^{[Notes 8]}. Al-Mahra tribes were experts in camelry and famed for their high-class Mehri camel breed which were renowned for their speed, agility and toughness.^[110]

Camel corpse bridge in al-Anbar

During the Battle of al-Anbar, Khalid instructed his soldiers to slaughter many sickly camels and throw them into the trench dug by the Persian defenders in front of the wall of Anbar fortress. The heap of dead camels served as a bridge for Khalid cavalry to cross the trench and breach the fortress.^{[Notes 9]}

Khalid's legendary camels' desert crossing

A map showing one of a series of possible itineraries of Khalid's march to Syria from Iraq

Around 634, after the clash at the Battle of Firaz against intercepting Byzantine forces, caliph Abu Bakr immediately instructed Khalid to reinforce the contingents of Abu Ubaydah, Amr ibn al-As, and Yazid ibn Abi Sufyan which started to invade Syria. Khalid immediately started his nearly impossible journey with his elite forces after leaving Muthanna ibn Haritha as his deputy in Iraq and instructed his soldiers to make each camel drink as much as possible before they started the six-day nonstop march without resupply.^{[146][Notes 10]} In the end, Khalid managed to reach Suwa spring and immediately defeated the Byzantine garrison in Arak, Syria,^[148] who were surprised by Khalid's force's sudden emergence from the desert.^[80]

According to Hugh Kennedy, historians across the ages assessed this daring journey with various expressions of amazement. Classical Muslim historians praised the marching force's perseverance as a miracle and work of god, while most western modern historians regard this as solely the genius of Khalid.^[149] It is Khalid, whose, in Hugh Kennedy's opinion, imaginative thinking effected this legendary feat.^[149] The historian Moshe Gil calls the march "a feat which has no parallel" and a testament to "Khalid's qualities as an outstanding commander".,^[150] while Laura Veccia Vaglieri and Patricia Crone^[151] dismissed the adventure of Khalid as never having happened as they thought it logically impossible.^[152] Nevertheless, military historian Richard G. Davis explained that Khalid imaginatively employed camel supply trains to make this journey possible.^[146] Those well hydrated camels that accompanied his journey were proven before in the Battle of Ullais for such a risky journey.^[144] Khalid resorted to slaughtering many camels for provisions for his desperate army.^[146]

Cavalry usage during siege warfare

The tactics used by Iyad in his Mesopotamian campaign were similar to those employed by the Muslims in Palestine, though in Iyad's case the contemporary accounts reveal his specific modus operandi, particularly in Raqqa.^[155] The operation to capture that city entailed positioning cavalry forces near its entrances, preventing its defenders and residents from leaving or rural refugees from entering.^[155] Concurrently, the remainder of Iyad's forces cleared the surrounding countryside of supplies and took captives.^[155] These dual tactics were employed in several other cities in al-Jazira.^[155] They proved effective in gaining surrenders from targeted cities running low on supplies and whose satellite villages were trapped by hostile troops.^[155]

Ubadah ibn al-Samit, another Rashidun commander, is also recorded to have developed his own distinct strategy which involved the use of cavalry during siege warfare. During a siege, Ubadah would dig a large hole, deep enough to hide a considerable number of horsemen near an enemy garrison, and hid his cavalry there during the night. When the sun rose and the enemy city opened their gates for the civilians in the morning, Ubadah and his hidden cavalry then emerged from the hole and stormed the gates as the unsuspecting enemy could not close the gate before Ubadah's horsemen entered. This strategy was used by Ubadah during the Siege of Laodicea^[156][157] and Siege of Alexandria.^[156]

Diwan al-Jund

Caliph Umar was the first ruler to organize the army state department in the name of Diwan al-Jund to oversee the needs of soldiers regarding equipment. This reform was introduced in 637 AD. A beginning was made with the Quraish and the Ansars and the system was gradually extended to the whole of Arabia and to Muslims of conquered lands. All adults who could be called to war were prepared, and a scale of salaries was fixed.^[99] All registered men were liable for military service. They were divided into two categories, namely:

1. Regular soldiers
2. Muslim civilians who could be enlisted for the compulsory call of Jihad in case of state emergency.^[99]

The pay was given in the beginning of the month of Muharram.

The armies of the Caliphs were mostly paid in cash salaries. In contrast to many post-Roman polities in Europe, grants of land, or rights to collect taxes directly from the people within one's grant of land, were of only minor importance. A major consequence of this was that the army directly depended on the state for its subsistence which, in turn, meant that the military had to control the state apparatus.^[162]

Roles within caliphate

Although they seem similar and interchangeable in duty, Haras and Shurta were different. Shurta mainly guarded and policed important state sites, such as Masjid Nabawi Caliphate citadel, the capital district of the Emirate governor, or Sultanate palaces, while also patrolling around the city to maintain law and punish any violations. Meanwhile, Haras served as bodyguards, whether to the prophet Muhammad himself, Caliphs, Sultans, Governors, or Amirs.^[165]

They were also tasked to assist the regular forces in battle to repel enemy advances toward the capital.^[163] This role was recorded by Ibn Kathir after the rebellion break out across Arabia after the death of the prophet, Abu Bakr immediately revived the organised elite guard unit al-Ḥaras wa al-Shurṭa, which had earlier been disbanded by the prophet himself after the Raid on Dhu Amarr. Abu Bakr raised these units again to defend Medina as a massive coalition of tribes had gathered around Medina while the main army of Medina had accompanied Usama ibn Zayd to conquer the border of northern Arabia and Jordan.^[165] Veteran companions such as Ali ibn Abi Talib, Talha ibn Ubayd Allah, Abd al-Rahman ibn Awf, Abdullah ibn Mas'ud and Zubair ibn al-Awwam were appointed as commanders of these units before the battle.^[166] This unit defeated the huge rebel tribes gathering during the defense of Medina, by only using transport camels as mounts, since warhorses and trained camels were brought by the main army led by Usama, who was still fighting the Ghassanid in the north.^[166]

After Abu Bakr, Haras and Shurta practice of retinual bodyguards seems absent or minimal during the reign of Umar, Uthman, Ali, and Hasan.^[165][163] However, after Mu'awiyah ascension he revived this practice drastically after the bloody ends of Umar, Uthman, Ali, and Hasan ibn Ali. Haras and Shurta broadened the role to not only guard caliph, but also Amirs or military governors which continued onwards of successive caliphates, both Umayyad and Abbasid, and their localized successor states.^[165] According to the tradition of Imam Suyuti, the first person to implement Shurta police forces on the governor level was Amr ibn al-'As.^[163]

Strength

Shurta bodyguard numbers varied from around 30-50 at the time of the prophet, or 500-600 at the time of Mu'awiyah. For Umayyad governors such as Khalid al-Qasri even possessed 4,000 members or higher for later era^[163] which practically became private armies of each governor.

Equipment

Shurta during Umayyad usually patrolled on horseback.^[163] Hajjaj ibn Yusuf prescribed that Shurta members must ride the best horses and forbade Shurta to ride inferior animals such as mules.^[163] The Shurta often wore heavy armor of Mujaffafa (scale armor) during their duty.^[163]

According to various early Muslim historians, aside from protecting the sovereign and capital, the Haras unit also acted as security police to maintain the safety of the city where they were assigned. During Umayyad rule they were armed with javelin-sized short spears called Hirba, a mace, along with whips and chains as disciplining weapon.^[165] They also usually carried Sayf long swords in order to immediately executes someone on the order of their superiors.^[163] The Shurta during the Umayyad period also carried a weapon called Kafr Kubat, a slingshot-type weapon^[163]