The large geographic area that connects the Strait of Gibraltar to the Indus River met in the seventh and eighth century changes of supreme importance due to the expansion of the Arabs and the spread of Islam, the new religion, inspired by Judaism and Christianity, preached by Mohammed in the first half of the seventh century.
To understand what kind of profound revolution Islam has caused in the Arab world, it is necessary to ask what was the pre-Islamic Arabia. A peninsula of about three million square miles, largely arid and covered by nomadic tribes of Bedouins polytheists who moved camel from oasis to another escorting merchant caravans and devoting themselves to the raid. It was Islam to turn this mosaic of the nomadic tribes of the Arabian desert in a combative people, united by faith in God and led by the Prophet Muhammad and his successors (Caliphs). In this perspective is particularly important the political and cultural operation performed by Muhammad, that after the flight to Medina (Hijr) from Mecca where he was persecuted (622) sublimate to the rank of holy war (jihad) the habit to raid of Bedouins. So it was that the use of raiding sedentary peoples settled in the oasis, turned into a desire to expand strong enough to allow the Arabs to conquer, in about a century, an immense empire.
In their expansion, after the death of the Prophet, is possible to distinguish two phases. At first (632-661), the holy war - also seen as a means to overcome the tribal conflicts within the Arabic world - had a quick and unexpected success: they conquered Syria, Egypt, Cyrenaica, Tripolitania, the Persian Empire. In the second phase, the Umayyad (644-656), the expansion was more fraught with difficulties, especially in Africa. Nevertheless, it went both to the east and towards the west, so that by the mid-eighth century the Arab empire stretched from the shores of the Atlantic to the Indus and embraced the Iberian peninsula, the southern tip of France, North Africa, Cyprus, Syria, Palestine, the Arabian Peninsula, Persia, Afghanistan, part of the basin of the Indus and Kyrgyzstan.
The irresistible advance of Islam into the heart of the Asian continent came until to inflict a famous military defeat in 751 to the Chinese empire in Talas, Kyrgyzstan. This expansion, then extended by the conquest of Crete and Sicily, was a fact of great importance for economic history. The rule of the Christian countries of the Mediterranean passed largely to the Arab world, which, to borrow a very widespread among historians, shook Europe in a "big catch" from the Caucasus to the Pyrenees. The reasons for this success must not, however, to be find only in the Islamic capabilities: the enthusiastic desire for conquest Bedouin converted by Muhammad knock down on empires, such as the Byzantine and Sasanid one, become more fragile by dangerous social lacerations due to the pressure came from an intolerable tax system and sometimes even from religious persecution. This is the case, the latter of Syria and Egypt, where it was widespread Monophysitism that Byzantium recurrently haunted.