: According to Muslim biographies, Muhammad, having received intelligence that Byzantine forces were concentrating in northern Arabia with intentions of invading Arabia, led a Muslim army north to
Tabuk in present-day northwestern
Saudi Arabia, with the intention of pre-emptively engaging the Byzantine army, however, the Byzantine army had retreated beforehand. Though it was not a
battle in the typical sense, nevertheless the event represented the first Arab encounter against the Byzantines. It did not, however, lead immediately to a military confrontation. 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 possibly referencing 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 offensive against both empires, resulting in the conquest of
Syria,
Egypt and
Persia for Islam. The most successful Arab 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 Arabs as liberators, as they were discontented with the rule of the Byzantines. The Roman Emperor
Heraclius had fallen ill and was unable to personally lead his armies to resist the Arab conquests of Syria and
Roman Palestine in 634. In a
battle fought near Ajnadayn in the summer of 634, the
Rashidun 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. The 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. 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. The fall of Alexandria extinguished Byzantine rule in Egypt, and allowed the Muslims to continue their military expansion into North Africa; between 643 and 644 'Amr completed the conquest of
Cyrenaica.
Uthman succeeded Caliph
Umar after his death. 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. 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. However, Crete reverted to Eastern Roman rule until the 820s.
Conquest of the Exarchate of Africa In 647, a Rashidun army led by
Abd Allah ibn Sa'd 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 the
First Muslim Civil War, the
Umayyads came to power in the Arab Empire under
Mu'awiya I. Under the Umayyads the conquest of the remaining Byzantine and northern Berber territories in North Africa was completed, enabling the Arabs to invade
Visigothic Spain through the
Strait of Gibraltar, 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. Mu'awiya 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 (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 religious centers in the
Middle Ages. Uqba "
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, Uqba ibn Nafi took the coastal cities of
Bejaia and
Tangier, overwhelming what had once been the
Roman province of
Mauretania 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 their ultimate objective. Their thinking was dominated by Islamic teaching, which placed the infidel Byzantines 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,
Mu'awiya ibn Abi Sufyan (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. To stop the Byzantine harassment from the sea during the Arab-Byzantine Wars, in 649 Mu'awiya set up a navy, manned by
Monophysitise Christian,
Copt and
Jacobite Syrian Christian sailors and Muslim troops. This resulted in the defeat of the Byzantine navy at the
Battle of the Masts in 655, opening up the Mediterranean. 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. 500 Byzantine ships were destroyed in the battle, and Emperor
Constans II was almost killed. By this point the detachment stationed at Jorus C’Baoth could no longer hold its position and was ordered to retreat. Under the instructions of
Caliph Uthman, Mu'awiya then prepared for the
siege of Constantinople. 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 commonplace; in early Islamic times the two countries were so remote that even the most basic information was unknown" (Kennedy). Mu'awiya 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.
Attacks against Byzantine holdings in Africa, Sicily and the East After his victory in the civil war, Mu'awiya 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, Mu'awiya 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
Abu Ayyub al-Ansari, 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. , his coinage still bore the traditional "
PAX",
peace. The setback at Constantinople was followed by further reverses across the vast 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. The wars of
Justinian II (r. 685–695 and 705–711), last emperor of the
Heraclian Dynasty, "reflected the general chaos of the age". Deposed in 695, with
Carthage lost in 698, Justinian returned to power from 705 to 711. His second reign was marked by Arab victories in Asia Minor and civil unrest. 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. of
Constantinople. 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 ==