Arab – Byzantine wars The Arab – Byzantine wars were a series of wars between the mostly Arab Muslims and the East Roman or Byzantine Empire between the 7th and 11th centuries AD . These started during the initial Muslim conquests under the expansionist Rashidun and Umayyad caliphs in the 7th century and continued by their successors until the mid - 11th century . The eruption of the Arabs from the Arab Peninsula in the 630s resulted in the rapid loss of Byzantium ' s southern provinces ( Syria and Egypt ) to the Muslims . Over the next fifty years , under the aggressive Umayyads caliphs , the Muslims would launch repeated raids into still - Byzantine Asia Minor , twice threaten the Byzantine capital , Constantinople , with conquest , and outright conquer the Byzantine Exarchate of Africa . The situation did not stabilize until after the failure of the Second Arab Siege of Constantinople in 718 , when the Taurus Mountains on the eastern rim of Asia Minor became established as the mutual , heavily fortified and largely depopulated frontier . Under the Abbasid Empire , relations became more normal , with embassies exchanged and even periods of truce , but conflict remained the norm , with almost annual raids and counter - raids , sponsored either by the Abbasid government or by local rulers , well into the 10th century . During the first centuries , the Byzantines were usually in the defensive , and avoided open field battles , preferring to retreat to their fortified strongholds . Only after 740 did they begin to launch counterstrikes of their own , but still the Abbasid Empire was able to retaliate by often massive and destructive invasions of Asia Minor . With the decline and fragmentation of the Abbasid state after 861 and the concurrent strengthening of the Byzantine Empire under the Macedonian dynasty , the tide gradually turned . Over a period of fifty years from ca . 920 to 976 , the Byzantines finally broke through the Muslim defences and restored their control over northern Syria and Greater Armenia . The last century of the Byzantine - Arab wars was dominated by frontier conflicts with the Fatimids in Syria , but the border remained stable until the appearance of a new people , the Seljuk Turks , after 1060 . The Muslims also took to the sea , and from the 650s on , the entire Mediterranean Sea became a battleground , with raids and counter - raids being launched against islands and the coastal settlements . Muslim raids reached a peak in the 9th and early 10th centuries , after their conquest of Crete , Malta and Sicily , with their fleets reaching the coasts of France , Dalmatia and even the suburbs of Constantinople . Background . The prolonged and escalating Byzantine – Sassanid wars of the 6th and 7th centuries left both empires exhausted and vulnerable in the face of the sudden emergence and expansion of the Arabs . The last of these wars ended with victory for the Byzantines : Emperor Heraclius regained all lost territories , and restored the True Cross to Jerusalem in 629 . Nevertheless , neither empire was given any chance to recover , as within a few years they were struck by the onslaught of the Arabs ( newly united by Islam ) , which , according to Howard - Johnston , " can only be likened to a human tsunami " . According to George Liska , the " unnecessarily prolonged Byzantine – Persian conflict opened the way for Islam " . In late 620s Muhammad had already managed to conquer and unify much of Arabia under Muslim rule , and it was under his leadership that the first Muslim - Byzantine skirmishes took place . Just a few months after Heraclius and the Persian general Shahrbaraz agreed on terms for the withdrawal of Persian troops from occupied Byzantine eastern provinces in 629 , Arab and Byzantine troops confronted each other at the Mu ' tah . Muhammad died in 632 and was succeeded by Abu Bakr , the first Caliph with undisputed control of the entire Arab peninsula after the successful Ridda Wars , which resulted in the consolidation of a powerful Muslim state throughout the peninsula . The Muslim conquests , 634 – 718 . According to Muslim biographies , Muhammed , having received intelligence that Byzantine forces were concentrating in northern Arabia with alleged intentions of invading Arabia , led a Muslim army north to Tabouk in present - day northwestern Saudi Arabia , with the intention of pre - emptively engaging the Byzantine army ; the news , however , proved to be false . Though it was not a battle in the typical sense , nevertheless the event represented the first Arab attack on the Byzantines . It did not , however , lead immediately to a military confrontation . However , there is no contemporary Byzantine account of the Tabuk expedition , and many of the details come from much later Muslim sources . It has been argued that there is in one Byzantine source a possible reference to the Battle of Mu´tah traditionally dated 629 , but this is not certain . The first engagements may have started as conflicts with the Arab client states of the Byzantine and Sassanid empires : the Ghassanids and the Lakhmids of Al - Hirah . In any case , Muslim Arabs after 634 certainly pursued a full - blown invasion of both empires , resulting in the conquest of the Levant , Egypt and Persia for Islam . The most successful generals were Khalid ibn al - Walid and ' Amr ibn al - ' As . Arab conquest of Roman Syria : 634 – 638 . In the Levant , the invading Rashidun army were engaged by a Byzantine army composed of imperial troops as well as local levies . According to Islamic historians Monophysites and Jews throughout Syria welcomed the Arab invaders , as they were discontented with Byzantine rule . The Arabian tribes also had significant economic , cultural and familial ties with predominantly Arab citizens of the Fertile Crescent . The Roman Emperor Heraclius had fallen ill and was unable to personally lead his armies to resist the Arab conquests of Syria and Palestine in 634 . In a battle fought near Ajnadayn in the summer of 634 , the Rashidun Caliphate army achieved a decisive victory . After their victory at the Fahl , Muslim forces conquered Damascus in 634 under the command of Khalid ibn al - Walid . Byzantine response involved the collection and dispatch of the maximum number of available troops under major commanders , including Theodore Trithyrius and the Armenian general Vahan , to eject the Muslims from their newly won territories . At the Battle of Yarmouk in 636 , however , the Muslims , having studied the ground in detail , lured the Byzantines into pitched battle , which the Byzantines usually avoided , and into a series of costly assaults , before turning the deep valleys and cliffs into a catastrophic death - trap . Heraclius ' farewell exclamation ( according to the 9th - century historian Al - Baladhuri ) while departing Antioch for Constantinople , is expressive of his disappointment : " Peace unto thee , O Syria , and what an excellent country this is for the enemy ! " The impact of Syria ' s loss on the Byzantines is illustrated by Joannes Zonaras ' words : " [ . . . ] since then [ after the fall of Syria ] the race of the Ishmaelites did not cease from invading and plundering the entire territory of the Romans " . In April 637 , the Arabs , after a long siege captured Jerusalem , which was surrendered by Patriarch Sophronius . In the summer of 637 , the Muslims conquered Gaza , and , during the same period , the Byzantine authorities in Egypt and Mesopotamia purchased an expensive truce , which lasted three years for Egypt and one year for Mesopotamia . Antioch fell to the Muslim armies in late 637 , and by then the Muslims occupied the whole of northern Syria , except for upper Mesopotamia , which they granted a one - year truce . At the expiration of this truce in 638 – 639 , the Arabs overran Byzantine Mesopotamia and Byzantine Armenia , and terminated the conquest of Palestine by storming Caesarea Maritima and effecting their final capture of Ascalon . In December 639 , the Muslims departed from Palestine to invade Egypt in early 640 . Arab conquests of North Africa : 639 – 698 . Conquest of Egypt and Cyrenaica . By the time Heraclius died , much of Egypt had been lost , and by 637 – 638 the whole of Syria was in the hands of the armies of Islam . With 3 , 500 – 4 , 000 troops under his command , ' Amr ibn al - A ' as first crossed into Egypt from Palestine at the end of 639 or the beginning of 640 . He was progressively joined by further reinforcements , notably 12 , 000 soldiers by Al - Zubayr . ' Amr first besieged and conquered Babylon , and then attacked Alexandria . The Byzantines , divided and shocked by the sudden loss of so much territory , agreed to give up the city by September 642 . The fall of Alexandria extinguished Byzantine rule in Egypt , and allowed the Muslims to continue their military expansion into North Africa ; between 643 – 644 ' Amr completed the conquest of Cyrenaica . Uthman succeeded Caliph Umar after his death . During his reign the Byzantine navy briefly won back Alexandria in 645 , but lost it again in 646 shortly after the Battle of Nikiou . The Islamic forces raided Sicily in 652 , while Cyprus and Crete were captured in 653 . According to Arab historians , the local Christian Copts welcomed the Arabs just as the Monophysites did in Jerusalem . The loss of this lucrative province deprived the Byzantines of their valuable wheat supply , thereby causing food shortages throughout the Byzantine Empire and weakening its armies in the following decades . Conquest of the Exarchate of Africa . In 647 , an Arab army led by Abdallah ibn al - Sa ’ ad invaded the Byzantine Exarchate of Africa . Tripolitania was conquered , followed by Sufetula , south of Carthage , and the governor and self - proclaimed Emperor of Africa Gregory was killed . Abdallah ' s booty - laden force returned to Egypt in 648 after Gregory ' s successor , Gennadius , promised them an annual tribute of some 300 , 000 " nomismata " . Following a civil war in the Arab Empire the Umayyads came to power under Muawiyah I . Under the Umayyads the conquest of the remaining Byzantine territories in North Africa was completed and the Arabs were able to move across large parts of Maghreb , invading Visigothic Spain through the Strait of Gibraltar , under the command of the Berber general Tariq ibn - Ziyad . But this happened only after they developed a naval power of their own , and they conquered and destroyed the Byzantine stronghold of Carthage between 695 – 698 . The loss of Africa meant that soon , Byzantine control of the Western Mediterranean was challenged by a new and expanding Arab fleet , operating from Tunisia . Muawiyah began consolidating the Arab territory from the Aral Sea to the western border of Egypt . He put a governor in place in Egypt at al - Fustat , and launched raids into Anatolia in 663 . Then from 665 to 689 a new North African campaign was launched to protect Egypt " from flank attack by Byzantine Cyrene " . An Arab army of 40 , 000 took Barca , defeating 30 , 000 Byzantines . A vanguard of 10 , 000 Arabs under Uqba ibn Nafi followed from Damascus . In 670 , Kairouan in modern Tunisia was established as a base for further invasions ; Kairouan would become the capital of the Islamic province of Ifriqiya , and one of the main Arabo - Islamic cultural centers in the Middle Ages . Then ibn Nafi " plunged into the heart of the country , traversed the wilderness in which his successors erected the splendid capitals of Fes and Morocco , and at length penetrated to the verge of the Atlantic and the great desert . In his conquest of the Maghreb , he took the coastal cities of Bugia and Tingi , overwhelming what had once been the Roman province of Mauretania Tingitana where he was finally halted . As the historian Luis Garcia de Valdeavellano explains : Arab attacks on Anatolia and sieges of Constantinople . As the first tide of the Muslim conquests in the Near East ebbed off , and a semi - permanent border between the two powers was established , a wide zone , unclaimed by either Byzantines or Arabs and virtually deserted ( known in Arabic as " al - Ḍawāḥī " , " the outer lands " and in Greek as , " ta akra " , " the extremities " ) emerged in Cilicia , along the southern approaches of the Taurus and Anti - Taurus mountain ranges , leaving Syria in Muslim and the Anatolian plateau in Byzantine hands . Both Emperor Heraclius and the Caliph ' Umar ( r . 634 – 644 ) pursued a strategy of destruction within this zone , trying to transform it into an effective barrier between the two realms . Nevertheless , the Umayyads still considered the complete subjugation of Byzantium as its ultimate objective . Their thinking was dominated by Islamic teaching , which placed the infidel Byzantines firmly in the " Dār al - Ḥarb " , the " House of War " , which , in the words of Islamic scholar Hugh N . Kennedy , " the Muslims should attack whenever possible ; rather than peace interrupted by occasional conflict , the normal pattern was seen to be conflict interrupted by occasional , temporary truce ( " hudna " ) . True peace ( " ṣulḥ " ) could only come when the enemy accepted Islam or tributary status . " Both as governor of Syria and later as caliph , Muawiyah I ( r . 661 – 680 ) was the driving force of the Muslim effort against Byzantium , especially by his creation of a fleet , which challenged the Byzantine navy and raided the Byzantine islands and coasts . The shocking defeat of the imperial fleet by the young Muslim navy at the Battle of the Masts in 655 was of critical importance : it opened up the Mediterranean , hitherto a " Roman lake " , to Arab expansion , and began a centuries - long series of naval conflicts over the control of the Mediterranean waterways . Trade between the Muslim eastern and southern shores and the Christian northern shores almost ceased during this period , isolating Western Europe from developments in the Muslim world : " In antiquity , and again in the high Middle Ages , the voyage from Italy to Alexandria was a commonplace ; in early Islamic times the two countries were so remote that even the most basic information was unknown " ( Kennedy ) . Muawiyah also initiated the first large - scale raids into Anatolia from 641 on . These expeditions , aiming both at plunder and at weakening and keeping the Byzantines at bay , as well as the corresponding retaliatory Byzantine raids , eventually became established as a fixture of Byzantine – Arab warfare for the next three centuries . The outbreak of the Muslim Civil War in 656 bought a precious breathing pause for Byzantium , which Emperor Constans II ( r . 641 – 668 ) used to shore up his defences , extend and consolidate his control over Armenia and most importantly , initiate a major army reform with lasting effect : the establishment of the " thema ta " , the large territorial commands into which Anatolia , the major contiguous territory remaining to the Empire , was divided . The remains of the old field armies were settled in each of them , and soldiers were allocated land there in payment of their service . The " themata " would form the backbone of the Byzantine defensive system for centuries to come . Attacks against Byzantine holdings in Africa , Sicily and the East . After his victory in the civil war , Muawiyah launched a series of attacks against Byzantine holdings in Africa , Sicily and the East . By 670 , the Muslim fleet had penetrated into the Sea of Marmara and stayed at Cyzicus during the winter . Four years later , a massive Muslim fleet reappeared in the Marmara and re - established a base at Cyzicus , from there they raided the Byzantine coasts almost at will . Finally in 676 , Muawiyah sent an army to invest Constantinople from land as well , beginning the First Arab Siege of the city . Constantine IV ( r . 661 – 685 ) however used a devastating new weapon that came to be known as " Greek fire " , invented by a Christian refugee from Syria named Kallinikos of Heliopolis , to decisively defeat the attacking Umayyad navy in the Sea of Marmara , resulting in the lifting of the siege in 678 . The returning Muslim fleet suffered further losses due to storms , while the army lost many men to the thematic armies who attacked them on their route back . Among those killed in the siege was Eyup , the standard bearer of Muhammed and the last of his companions ; to Muslims today , his tomb is considered one of the holiest sites in Istanbul . The Byzantine victory over the invading Umayyads halted the Islamic expansion into Europe for almost thirty years . The setback at Constantinople was followed by further reverses across the huge Muslim empire . As Gibbon writes , " this Mahometan Alexander , who sighed for new worlds , was unable to preserve his recent conquests . By the universal defection of the Greeks and Africans he was recalled from the shores of the Atlantic . " His forces were directed at putting down rebellions , and in one such battle he was surrounded by insurgents and killed . Then , the third governor of Africa , Zuheir , was overthrown by a powerful army , sent from Constantinople by Constantine IV for the relief of Carthage . Meanwhile , a second Arab civil war was raging in Arabia and Syria resulting in a series of four caliphs between the death of Muawiyah in 680 and the ascension of Abd al - Malik in 685 , and was ongoing until 692 with the death of the rebel leader . The Saracen Wars of Justinian II ( r . 685 – 695 and 705 – 711 ) , last emperor of the Heraclian Dynasty , " reflected the general chaos of the age " . After a successful campaign he made a truce with the Arabs , agreeing on joint possession of Armenia , Iberia and Cyprus ; however , by removing 12 , 000 Christian Mardaites from their native Lebanon , he removed a major obstacle for the Arabs in Syria , and in 692 , after the disastrous Battle of Sebastopolis , the Muslims invaded and conquered all of Armenia . Deposed in 695 , with Carthage lost in 698 , Justinian returned to power from 705 - 711 . His second reign was marked by Arab victories in Asia Minor and civil unrest . Reportedy , he ordered his guards to execute the only unit that had not deserted him after one battle , to prevent their desertion in the next . Justinian ' s first and second depositions were followed by internal disorder , with successive revolts and emperors lacking legitimacy or support . In this climate , the Umayyads consolidated their control of Armenia and Cilicia , and began preparing a renewed offensive against Constantinople . In Byzantium , the general Leo the Isaurian ( r . 717 – 741 ) had just seized the throne in March 717 , when the massive Muslim army under the famed Umayyad prince and general Maslama ibn Abd al - Malik began moving towards the imperial capital . The Caliphate ' s army and navy , led by Maslama , numbered some 120 , 000 men and 1 , 800 ships according to the sources . Whatever the real number , it was a huge force , far larger than the imperial army . Thankfully for Leo and the Empire , the capital ' s sea walls had recently been repaired and strengthened . In addition , the emperor concluded an alliance with the Bulgar khan Tervel , who agreed to harass the invaders ' rear . From July 717 to August 718 , the city was besieged by land and sea by the Muslims , who built an extensive double line of circumvallation and contravallation on the landward side , isolating the capital . Their attempt to complete the blockade by sea however failed when the Byzantine navy employed Greek fire against them ; the Arab fleet kept well off the city walls , leaving Constantinople ' s supply routes open . Forced to extend the siege into winter , the besieging army suffered horrendous casualties from the cold and the lack of provisions . In spring , new reinforcements were sent by the new caliph , Umar ibn Abd al - Aziz ( r . 717 – 720 ) , by sea from Africa and Egypt and over land through Asia Minor . The crews of the new fleets were composed mostly of Christians , who began defecting in large numbers , while the land forces were ambushed and defeated in Bithynia . As famine and an epidemic continued to plague the Arab camp , the siege was abandoned on 15 August 718 . On its return , the Arab fleet suffered further casualties to storms and an eruption of the volcano of Thera . Stabilization of the frontier , 718 – 863 . The first wave of the Muslim conquests ended with the siege of Constantinople in 718 , and the border between the two empires became stabilized along the mountains of eastern Anatolia . Raids and counter - raids continued on both sides and became almost ritualized , but the prospect of outright conquest of Byzantium by the Caliphate receded . This led to far more regular , and often friendly , diplomatic contacts , as well as a reciprocal recognition of the two empires . In response to the Muslim threat , which reached its peak in the first half of the 8th century , the Isaurian emperors adopted the policy of Iconoclasm , which was abandoned in 786 only to be readopted in the 820s and finally abandoned in 843 . Under the Macedonian dynasty , exploiting the decline and fragmentation of the Abbasid Caliphate , the Byzantines gradually went into the offensive , and recovered much territory in the 10th century , which was lost however after 1071 to the Seljuk Turks . Raids under the last Umayyads and the rise of Iconoclasm . Following the failure to capture Constantinople in 717 – 718 , the Umayyads for a time diverted their attention elsewhere , allowing the Byzantines to take to the offensive , making some gains in Armenia . From 720 / 721 however the Arab armies resumed their expeditions against Byzantine Anatolia , although now they were no longer aimed at conquest , but rather large - scale raids , plundering and devastating the countryside and only occasionally attacking forts or major settlements . Under the late Umayyad and early Abbasid caliphs , the frontier between Byzantium and the Caliphate became stabilized along the line of the Taurus - Antitaurus mountain ranges . On the Arab side , Cilicia was permanently occupied and its deserted cities , such as Adana , Mopsuestia ( al - Massisa ) and , most importantly , Tarsus , were refortified and resettled under the early Abbasids . Likewise , in Upper Mesopotamia , places like Germanikeia ( Mar ' ash ) , Hadath and Melitene ( Malatya ) became major military centers . These two regions came to form the two halves of a new fortified frontier zone , the " thughur " . Both the Umayyads and later the Abbasids continued to regard the annual expeditions against the Caliphate ' s " traditional enemy " as an integral part of the continuing " jihad " , and they quickly became organized in a regular fashion : one to two summer expeditions ( pl . " ṣawā ' if " , sing . " ṣā ' ifa " ) sometimes accompanied by a naval attack and / or followed by winter expeditions ( " shawātī " ) . The summer expeditions were usually two separate attacks , the " expedition of the left " ( " al - ṣā ' ifa al - yusrā / al - ṣughrā " ) launched from the Cilician " thughur " and consisting mostly of Syrian troops , and the usually larger " expedition of the right " ( " al - ṣā ' ifa al - yumnā / al - kubrā " ) launched from Malatya and composed of Mesopotamian troops . The raids were also largely confined to the borderlands and the central Anatolian plateau , and only rarely reached the peripheral coastlands , which the Byzantines fortified heavily . Under the more aggressive Caliph Hisham ibn Abd al - Malik ( r . 723 – 743 ) , the Arab expeditions intensified for a time , and were led by some of the Caliphate ' s most capable generals , including princes of the Umayyad dynasty like Maslama ibn Abd al - Malik and al - Abbas ibn al - Walid or Hisham ' s own sons Mu ' awiyah , Maslama and Sulayman . This was still a time when Byzantium was fighting for survival , and " the frontier provinces , devastated by war , were a land of ruined cities and deserted villages where a scattered population looked to rocky castles or impenetrable mountains rather than the armies of the empire to provide a minimum of security " ( Kennedy ) . In response to the renewal of Arab invasions , and to a sequence of natural disasters such as the eruptions of the volcanic island of Thera , the Emperor Leo III the Isaurian concluded that the Empire had lost divine favour . Already in 722 he had tried to force the conversion of the Empire ' s Jews , but soon he began to turn his attention to the veneration of icons , which some bishops had come to regard as idolatrous . In 726 , Leo published an edict condemning their use and showed himself increasingly critical of the iconophile s . He formally banned depictions of religious figures in a court council in 730 . This decision provoked major opposition both from the people and the church , especially the Bishop of Rome , which Leo did not take into account . In the words of Warren Treadgold : " He saw no need to consult the church , and he appears to have been surprised by the depth of the popular opposition he encountered " . The controversy weakened the Byzantine Empire , and was a key factor in the schism between the Patriarch of Constantinople and the Bishop of Rome . The Umayyad Caliphate however was increasingly distracted by conflicts elsewhere , especially its confrontation with the Khazars , with whom Leo III had concluded an alliance , marrying his son and heir , Constantine V ( r . 741 – 775 ) to the Khazar princess Tzitzak . Only in the late 730s did the Muslim raids again become a threat , but the great Byzantine victory at Akroinon and the turmoil of the Abbasid Revolution led to a pause in Arab attacks against the Empire . It also opened up the way for a more aggressive stance by Constantine V ( r . 741 – 775 ) , who in 741 attacked the major Arab base of Melitene , and continued scoring further victories . These successes were also interpreted by Leo III and his son Constantine as evidence of God ' s renewed favour , and strengthened the position of Iconoclasm within the Empire . The early Abbasids . Unlike their Umayyad predecessors , the Abbasid caliphs did not pursue active expansion : in general terms , they were content with the territorial limits achieved , and whatever external campaigns they waged were retaliatory or preemptive , meant to preserve their frontier and impress Abbasid might upon their neighbours . At the same time , the campaigns against Byzantium in particular remained important for domestic consumption . The annual raids , which had almost lapsed in the turmoil following the Abbasid Revolution , were undertaken with renewed vigour from ca . 780 on , and were the only expeditions where the Caliph or his sons participated in person . As a symbol of the Caliph ' s ritual role as the leader of the Muslim community , they were closely paralleled in official propaganda by the leadership by Abbasid family members of the annual pilgrimage ( " hajj " ) to Mecca . In addition , the constant warfare on the Syrian marches was useful to the Abbasids as it provided employment for the Syrian and Iraqi military elites and the various volunteers ( " muṭṭawi ‘ a " ) who flocked to participate in the " jihad " . Wishing to emphasize his piety and role as the leader of the Muslim community , Caliph Harun al - Rashid ( r . 786 – 809 ) in particular was the most energetic of the early Abbasid rulers in his pursuit of warfare against Byzantium : he established his seat at Raqqa close to the frontier , he complemented the " thughur " in 786 by forming a second defensive line along northern Syria , the " al - ' Awasim " , and was reputed to be spending alternating years leading the " Hajj " and leading a campaign into Anatolia , including the largest expedition assembled under the Abbasids , in 806 . Continuing a trend started by his immediate predecessors , his reign also saw the development of far more regular contacts between the Abbasid court and Byzantium , with the exchange of embassies and letters being far more common than under the Umayyad rulers . Despite Harun ' s hostility , " the existence of embassies is a sign that the Abbasids accepted that the Byzantine empire was a power with which they had to deal on equal terms " ( Kennedy ) . Civil war occurred in the Byzantine Empire , often with Arab support . With the support of Caliph Al - Ma ' mun , Arabs under the leadership of Thomas the Slav invaded , so that within a matter of months , only two " themata " in Asia Minor remained loyal to Emperor Michael II . When the Arabs captured Thessalonica , the Empire ' s second largest city , it was quickly re - captured by the Byzantines . Thomas ' s 821 siege of Constantinople did not get past the city walls , and he was forced to retreat . The Arabs did not relinquish their designs on Asia Minor and in 838 began another invasion , sacking the city of Amorion . Sicily , Italy and Crete . While a relative equilibrium reigned in the East , the situation in the western Mediterranean was irretrievably altered when the Aghlabids began their slow conquest of Sicily in the 820s . Using Tunisia as their launching pad , the Arabs started by conquering Palermo in 831 , Messina in 842 , Enna in 859 , culminating in the capture of Syracuse in 878 . This in turn opened up southern Italy and the Adriatic Sea for raids and settlement . Byzantium further suffered an important setback with the loss of Crete to a band of Andalusian exiles , who established a piratical emirate on the island and for more than a century ravaged the coasts of the hitherto secure Aegean Sea . Byzantine resurgence , 863 – 11th century . Religious peace came with the emergence of the Macedonian dynasty in 867 , as well as a strong and unified Byzantine leadership ; while the Abassid empire had splintered into many factions afer 861 . Basil I revived the Byzantine Empire into a regional power , during a period of territorial expansion , making the Empire the strongest power in Europe , with an ecclesiastical policy marked by good relations with Rome . Basil allied with the Holy Roman Emperor Louis II against the Arabs , and his fleet cleared the Adriatic Sea from their raids . With Byzantine help , Louis II captured Bari from the Arabs in 871 . The city became Byzantine territory in 876 . The Byzantine position on Sicily deteriorated , and Syracuse fell to the Emirate of Sicily in 878 . Catania was lost in 900 , and finally the fortress of Taormina in 902 . Michael of Zahumlje apparently on 10 July 926 sacked Siponto ( ) , which was a Byzantine town in Apulia . It remains unknown whether Michael did so under King Tomislav ' s supreme command , as suggested by some historians . According to Omrčanin , Tomislav sent the Croatian navy under Michael ' s leadership to drive the Saracens from that part of southern Italy and free the city . Sicily would remain under Arab control until the Norman invasion in 1071 . Although Sicily was lost , the general Nikephoros Phokas the Elder succeeded in taking Taranto and much of Calabria in 880 , forming the nucleus for the later Catepanate of Italy . The successes in the Italian Peninsula opened a new period of Byzantine domination there . Above all , the Byzantines were beginning to establish a strong presence in the Mediterranean Sea , and especially the Adriatic . Under John Kourkouas , the Byzantines conquered the emirate of Melitene , along with Tarsos the strongest of the Muslim border emirates , and advanced into Armenia in the 930s ; the next three decades were dominated by the struggle of the Phokas clan and their dependants against the Hamdanid emir of Aleppo , Sayf al - Dawla . Al - Dawla was finally defeated by Nikephoros II Phokas , who conquered Cilicia and northern Syria and recovered Crete . His nephew and successor , John I Tzimiskes , pushed even further south , almost reaching Jerusalem , but his death in 976 ended Byzantine expansion towards Palestine . After putting an end to the internal strife , Basil II launched a counter - campaign against the Arabs in 995 . The Byzantine civil wars had weakened the Empire ' s position in the east , and the gains of Nikephoros II Phokas and John I Tzimiskes came close to being lost , with Aleppo besieged and Antioch under threat . Basil won several battles in Syria , relieving Aleppo , taking over the Orontes valley , and raiding further south . Although he did not have the force to drive into Palestine and reclaim Jerusalem , his victories did restore much of Syria to the empire — including the larger city of Antioch which was the seat of its eponymous Patriarch . No Byzantine emperor since Heraclius had been able to hold these lands for any length of time , and the Empire would retain them for the next 110 years until 1078 . Piers Paul Read writes that by 1025 , Byzantine land " stretched from the Straits of Messina and the northern Adriatic in the west to the River Danube and Crimea in the north , and to the cities of Melitine and Edessa beyond the Euphrates in the east . " Under Basil II , the Byzantines established a swath of new " themata " , stretching northeast from Aleppo ( a Byzantine protectorate ) to Manzikert . Under the Theme system of military and administrative government , the Byzantines could raise a force at least 200 , 000 strong , though in practice these were strategically placed throughout the Empire . With Basil ' s rule , the Byzantine Empire reached its greatest height in nearly five centuries , and indeed for the next four centuries . Conclusion . The wars drew near to a closure when the Turks and various Mongol invaders replaced the threat of either power . From the 11th and 12th centuries onwards , the Byzantine conflicts shifted into the Byzantine - Seljuk wars with the continuing Islamic invasion of Anatolia being taken over by the Seljuk Turks . After the defeat at the Battle of Manzikert by the Turks in 1071 , the Byzantine Empire , with the help of Western Crusade rs , re - established its position in the Middle East as a major power . Meanwhile , the major Arab conflicts were in the Crusades , and later against Mongolian invasions , especially that of the Golden Horde and Timur . Effects . As with any war of such length , the drawn - out Byzantine – Arab Wars had long lasting effects for both the Byzantine Empire and the Arab states . The Byzantines experienced extensive territorial loss , while the invading Arabs gained strong control in the Middle East and Africa . The focus of the Byzantine Empire shifted from the western reconquests of Justinian to a primarily defensive position , against the Islamic armies on its eastern borders . Without Byzantine interference in the emerging Christian states of western Europe , the situation gave a huge stimulus to feudalism and economic self - sufficiency . The view of modern historians is that one of the most important effects was the strain it put on the relationship between Rome and Byzantium . While fighting for survival against the Islamic armies , the Empire was no longer able to provide the protection it had once offered to the Papacy ; worse still , according to Thomas Woods , the Emperors " routinely intervened in the life of the Church in areas lying clearly beyond the state ' s competence " . The Iconoclast controversy of the 8th and 9th centuries can be taken as a key factor " which drove the Latin Church into the arms of the Franks . " Thus it has been argued that Charlemagne was an indirect product of Muhammad : The Holy Roman Empire of Charlemagne ' s successors would later come to the aid of the Byzantines under Louis II and during the Crusades , but relations between the two empires would be strained ; based on the " Salerno Chronicle " , we know the Emperor Basil had sent an angry letter to his western counterpart , reprimanding him for usurping the title of emperor . He argued that the Frankish rulers were simple " reges " , and that each nation has its own title for the ruler , whereas the imperial title suited only the ruler of the Eastern Romans , Basil himself . Historiography and other sources . Walter Emil Kaegi states that extant Arabic sources have been given much scholarly attention for issues of obscurities and contradictions . However , he points out that Byzantine sources are also problematic , such as the chronicles of Theophanes and Nicephorus and those written in Syriac , which are short and terse while the important question of their sources and their use of sources remains unresolved . Kaegi concludes that scholars must also subject the Byzantine tradition to critical scrutiny , as it " contains bias and cannot serve as an objective standard against which all Muslim sources may be confidently checked " . Among the few Latin sources of interest are the 7th century history of Fredegarius , and two 8th - century Spanish chronicles , all of which draw on some Byzantine and oriental historical traditions . As far as Byzantine military action against the initial Muslim invasions , Kaegi asserts that " Byzantine traditions . . . attempt to deflect criticism of the Byzantine debacle from Heraclius to other persons , groups , and things " . The range of non - historical Byzantine sources is vast : they range from papyri to sermons ( most notable those of Sophronius and Anastasius Sinaita ) , poetry ( especially that of Sophronius and George of Pisidia ) , correspondence often of a patristic provenance , apologetical treatises , apocalypses , hagiography , military manuals ( in particular the " Strategikon " of Maurice from the beginning of the 7th century ) , and other non - literary sources , such as epigraphy , archeology , and numismatics . None of these sources contains a coherent account of any of the campaigns and conquests of the Muslim armies , but some do contain invaluable details that survive nowhere else .