Caliphates and the Expansion of the Islamic World

Within a century of Muhammad's death, Muslim rule stretched from Spain to Central Asia. The first four 'rightly guided' caliphs conquered much of the Byzantine and Sasanian Persian empires, which had exhausted each other in war. The Umayyad dynasty (661–750), based in Damascus, expanded into North Africa, Spain and Sind; the Abbasids (750–1258), who founded Baghdad in 762, presided over a flourishing commercial and intellectual civilization.

Historians distinguish conquest from conversion: conquered peoples were not generally forced to convert, and Jews and Christians often lived as protected dhimmis, paying a poll tax (jizya) with restrictions but considerable communal autonomy. Conversion happened gradually over centuries, and many regions did not have Muslim majorities until long after conquest. Later, Islam spread to West Africa, the Indian Ocean and Southeast Asia mainly through traders and Sufi teachers rather than armies.

The Mongol sack of Baghdad in 1258 ended the Abbasid caliphate in its classic form.