This week Neil Faulkner describes the rise and explosive spread of the third great monotheistic religion, where compassion, charity, and protection became moral imperatives – Islam.

Turmoil is intellectually fertile. It created each of the great religions. Judaism was forged in the struggle of an embattled ruling class to establish itself in Palestine in the 6th century BC. Christianity has its origins in the bitterness of the oppressed under Roman imperial rule during the 1st century AD.

Islam was a third branch from the same stem. Its early growth, in the 620s AD, took place beneath the gaze of history, a matter of minor squabbles in two remote desert towns in the Hijaz region of western-central Arabia. But its violent eruption in the 630s AD would change the world forever.

The Huns had been steppe nomads without any leavening of towns, merchants, and urban culture. Cut adrift from the lifeways of the steppe, they were weightless. Because of this, their military blitzkrieg flashed across dying antiquity and, equally suddenly, was extinguished without trace.

Not so the Arabs. The desert nomads, herders of sheep and goats, breeders of camels and horses, were much like the Huns. But the camel, domesticated about 1000 BC, could cross great expanses of desert carrying heavy burdens, and many of the camel-breeders had become merchants.

The luxury goods traded through Mesopotamia and the Gulf, through Southern Arabia and the Red Sea, were carried west and north on Arab camel-caravans. Mecca, Medina, and other Arabian towns grew rich on trade.

The towns, along with other oases on the desert routeways, were also home to communities of artisans and cultivators.

There were, in short, in contrast to the steppe, complex settlements, social classes, and urban culture. In particular, co-existing with the tribal customs, oral traditions, and polytheistic beliefs of the desert nomads, there was the written Arabic and Judaeo-Christian religion of traders and townsmen.

Often, too, there was conflict. Long-distance trade cut across ties of kinship and tribal allegiances. The desert raid was booty to the tribesman, but robbery to the trader. The tribal blood-feud offered protection to local kinsfolk, but none to a trader in a distant town.

In places like Mecca and Medina, where nomads and peasants bartered, tribesmen and traders squabbled, and the traditions of desert and town collided, men and women discussed how the world worked – or rather, how it should work. When they did this, they viewed matters in a religious frame. For, in the early medieval world, to consider such things was to reflect on God’s intent.

Amid the ferment, and experiencing it as inner mental anguish, was a young man of a minor Meccan merchant family. He had visions, and believed God (or Allah in Arabic) spoke directly to him. He persuaded a small group of followers that this was so, and some of them began to write down the words he reported Allah as saying.

The Prophet’s name was Muhammad, and his reports of Allah’s words became the Koran.

Islam retained many Judaeo-Christian myths and traditions. Abraham and Moses are prophets for Jews, Christians, and Muslims alike. Also common to all three great religions was their universalism. Islam cut through tribal codes and class differences like a razor.

In place of the many competing gods of rival tribes, there was now one supreme deity. Where clan loyalty and the blood feud had reigned, there were now universal rules of conduct. Instead of abuse of the oppressed – women, slaves, the poor, the marginal – being a matter of indifference, compassion, charity, and protection became moral imperatives.

The Muslims formed a community (umma) based on formal equality, universal rights, and a single code of laws. Islam was an attempt to create order in a world of faction.

Little wonder that Muhammad encountered fierce opposition. His mission began around AD 620, but he was driven out of Mecca in AD 622 and forced to find refuge in Medina.

There, he built a small mass movement. To his growing politico-religious cadre of eager young men and women, he joined traders seeking commercial advantage, tribal leaders bent on plunder, and townsmen and peasants desirous of peace and order.

Returning to Mecca with an army in AD 630, he was victorious, and the Muslims took control of western-central Arabia.

When Muhammad died in AD 632, his movement might have disintegrated, torn apart by the traditional raiding and feuding of the desert tribes. But it did not, for the first two ‘caliphs’ (successors) – Abu Bakr and Umar – chose to direct the violent energy of Arabia against external targets: the Persian and Byzantine Empires.

When the Arab-Islamic armies struck, the old empires shattered like glass baubles. The great cities of antiquity fell like dominoes – Damascus (in Syria) in AD 636, Ctesiphon (Iraq) in AD 637, Babylon-Cairo (Egypt) in AD 639, and Alexandria (Egypt) in AD 642. Within ten years of their leader’s death, the followers of Muhammad had created a huge Middle Eastern empire.

As the Huns and Goths had done in Europe two centuries before, the Arabs had found the old empires, for all their pomp, hollow.

The Persian and Byzantine Empires had engaged in massive (and ultimately inconclusive) wars for centuries. The most recent, between AD 613 and 628, had left both exhausted, their finances depleted, manpower decimated, and populations embittered by taxation, conscription, and forced requisitions.

The Empires had fortifications, armoured warriors, and high-tech weaponry. The Arabs had the desert and the camel.

The Arabian desert projects northwards, a tongue of desiccated sand and gravel, between (Byzantine) Syria in the west and (Persian) Iraq in the east. In these wastes, the camel is supreme, and armies mounted on camels can move like ships at sea.

From the desert, suddenly, anywhere, the Arabs would emerge. When they did, lightly equipped and highly mobile, they would destroy the ponderous armies of tight-packed foot and heavy horse deployed against them in a dust of swirling manoeuvres.

The sullen peasants of Syria and Iraq cared nothing for the defeat of their masters. Often, they welcomed the Arabs as liberators. Many of the old landlords were gone. Taxes were lower. Judaism, Christianity, and Persian Zoroastrianism were tolerated; many, anyway, soon converted to Islam. Arab rule, by and large, meant improvement.

The Arab conquests continued. Arab armies swept along the North African coast, taking Libya, Tunisia, Algeria, and Morocco, and finally entering Spain, which was completely overrun by AD 711. Meantime, other armies had pushed east; Kabul in Afghanistan fell to Islam as early as AD 664.

It had been one of the most extensive, sudden, and transformative campaigns of military conquest in history. But in transforming the world, the conquerors had also transformed themselves – processes that were contradictory and contested.

The people of the desert, nomads, traders, and raiders, first exploded across the Middle East and North Africa. Then, having inherited the riches of the ancient world, they imploded in acrimony, murder, and civil war – as we shall see.