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"Spread of Islam, The." In Atlas of the World’s Religions, Second Edition. Ed. Ninian Smart, Frederick Denny. Oxford Islamic Studies Online. May 22, 2022. <>.


"Spread of Islam, The." In Atlas of the World’s Religions, Second Edition. , edited by Ninian Smart, Frederick Denny. Oxford Islamic Studies Online, (accessed May 22, 2022).

Spread of Islam, The

WTH THE DEATH of Muhammad, the Muslim community found itself without a leader. While as the ‘seal of the prophets’ he could have no successor, as a political guide Muhammad was succeeded by the so-called al Khulafa' al Rashidun, the four ‘rightly-guided caliphs’ who were chosen from his most loyal companions. It was during the leadership of these caliphs ( 632 – 56 ), and particularly under the second caliph and great statesman ‘Umar ibn al Khattab (634–44), that the conquest of territories outside Arabia began. Influenced by the political systems of these conquered areas, the leadership became hereditary, and the Umayyad dynasty ( 661 – 750 ) emerged out of the aristocracy of the Quraysh. While the Rashidun caliphs were based at Mecca and Medina, the Umayyads moved the seat of power to Damascus. Their successors, the ‘Abbasids ( 750 – 1258 ), who were less Arab-centred, built a new capital, Baghdad, in a fertile area on the main routes between Iraq, Iran and Syria.

The History of the Conquests

The Arab conquests started as sporadic tribal raids. A proper army was probably not organized before 634 , but once formed, it made expeditions eastwards towards the Sasanian empire and northwards to Palestine and Syria against the Byzantine empire.

Spread of Islam, The

1. Islamic Expansion to 750

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Under the leadership of commanders such as ‘Amr ibn al ‘As and Khalid ibn al Walid, the army defeated the Byzantines at Yarmuk ( 636 ), and the newly organized Muslim navy destroyed the Christian fleet at the Battle of the Masts ( 655 ). Constantinople was sporadically besieged during this period, though never captured. On the oriental front, the Sasanian army suffered a crushing defeat at the battle of al Qadisiyah ( 637 ), and Ctesiphon was taken soon afterwards; this caused the disintegration of the Sasanian empire. ‘Amr ibn al ‘As then moved westwards towards Egypt in 639 , and by 646 Heliopolis and Alexandria had fallen. The city of Fustat was founded in 643 , and northeast Africa was occupied. From Alexandria, naval expeditions were launched against Cyprus and Sicily and under the Umayyad dynasty the Muslims emerged as a major seapower. The eighth century saw further expansions eastwards as far as the river Indus and the Sind region and westwards through northern Africa to Spain and France where the over-stretched army was stopped at the battle of Poitiers by Charles Martel .

The surprising speed at which the conquests took place can be attributed to the weakness of countries debilitated by long external conflicts (the Sasanian empire) or by the fragility of internal structure (Spain). There was also discontent with despotic leadership and heavy taxation among the local population, especially in Syria and Spain.

Army and Society

The expanding Muslim army was at first only composed of Arab tribal groups, mostly infantry and some cavalry forces. Gradually it transformed itself by recruiting locally during its campaigns. The role played by the mawali (‘converted non-Arab clients’), such as Berber warriors in the western campaign to Spain and, eastwards, Persians and Turks, is well-known. The Umayyad armies relied on elite Syrian corps and increased the role of the cavalry and especially of units in armour, though the infantry was predominant. The first Abbasid armies, on the other hand, relied mostly on Khurasani elite forces and, by the early ninth century, the cavalry became clearly dominant. From the eleventh century onwards the horse-back archery techniques of Central Asian and Turkish origin began to play a major role in Muslim warfare.

Muslim commanders left the social structure of the conquered territories almost intact by appointing local Muslim governors and relying on local administrative and financial systems. The populations were not converted en masse but in time the frequency of conversions increased. The reasons for embracing Islam ranged from a desire to come closer to the new masters and share their privileges, to an acknowledgment of, or belief in, the tolerant and syncretistic nature of the new faith. Tolerance, however, could only be granted to the Ahl al Kitab (‘the people of the Book’) that is, those people whom the Qur'an cites as having received revealed scripture: Jews, Christians and the ‘Sabians’. These could not, in principle, be forcibly converted (as could polytheists and disbelievers), and were guaranteed protection and religious autonomy against the payment of a special tax.

Islam in Spain

By the end of the first Muslim campaign into Spain ( 711 - 13 ) all but the northwest corner of the Iberian peninsula came under Arab rule.

Spread of Islam, The

2. Islamic Spain to the 13th Century

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When the Umayyad dynasty collapsed in Damascus at the hand of the ‘Abbasids, one of its few surviving princes, ‘Abd al Rahman I, moved to the far west and seized Cordova in 755 , founding the Umayyad dynasty of Spain which was to last for over 300 years. The achievements of this period are embodied in the building in 788 of the Great Mosque of Cordova, which became a vibrant centre of learning. In time, however, the central authority of the state declined and, by the early eleventh century, Spain had broken up into a multiplicity of small kingdoms. The Christian states of the north captured Toledo in 1085 and this marks, to some extent, the first step towards the Crusades of the Middle Ages (see pp. 162-163).

Islamic Spain then came under the rule of Berber dynasties such as the Almoravids ( 1056 – 1147 ) and the Almohads ( 1130 – 1269 ), who held the entire political power of the western lands of Islam. The coalition of Christian states eventually reduced the presence of Islam to a strip of country in the southeast around Granada where, for a further 250 years, the Nasrid dynasty ruled. The Alhambra (‘the red’ castle) at Granada, the architectural masterpiece of Western Islam, belongs to this last period of Muslim rule. In 1492 , Granada surrendered to the Christians and, within a few years, all Muslims (and Jews) were expelled from Spain. Islamic Spain had played an important role as the intellectual Muslim centre in the West, through which Far and Near Eastern as well as Greek and Arabic technical, scientific and philosophical knowledge reached medieval Europe.

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