Wars which, in the century after the death of Muhammad in 632, created an empire stretching from Spain to the Indus valley. Beginning as a jihad (holy war) against the apostasy of the Arabian tribes that had renounced Islam they acquired a momentum of their own as the Arabs, inspired by the prospect of vast booty and the belief that death in battle would gain them instant admission to paradise, confronted the waning power of Byzantium and Persia.

In Syria and Egypt the conquerors allowed both Christians and Jews to keep their faiths as dhimmi (protected peoples) upon payment of a discriminatory tax. Local resistance in Persia and North Africa made the conquests there slower. After the first civil war (656–61) the Arab capital was moved from Medina to Damascus by the Umayyads, and under the Abbasids to the new city of Baghdad where, with the encouragement of the caliphs Harun al‐Rashid and al‐Mamun (786–833 ad), Islamic culture flowered. The political unity of this empire was short‐lived—rival caliphates appeared in North Africa and Spain in the 9th and 10th centuries—but cultural coherence was maintained by the universality of the Arabic language and Islamic law (shariah), and by the traffic of traders, scholars, and pilgrims which these made possible.