In 637 A.D., only five years after the death of the Prophet Muhammad, Arab Muslims shattered the might of the Iranian Sassanians at the battle of Qadisiya, and the invaders began to reach into the lands east of Iran. By the middle of the eighth century, the rising Abbasid Dynasty was able to subdue the Arab invasion, putting an end to the prolonged struggle. Peace prevailed under the rule of the caliph Harun al Rashid (785-809) and his son, and learning flourished in such Central Asian cities as Samarkand. From the seventh through the ninth centuries, most inhabitants of what is present-day Afghanistan, Pakistan, southern parts of the former Soviet Union, and areas of northern India were converted to Sunni Islam.

In the eighth and ninth centuries ancestors of many of today's Turkic-speaking Afghans settled in the Hindu Kush area (partly to obtain better grazing land) and began to assimilate much of the culture and language of the Pashtun tribes already present there (see Ethnic Groups, ch. 2).

By the middle of the ninth century, Abbasid rule had faltered, and semi-independent states began to emerge throughout the empire. In the Hindu Kush area, three short-lived, local dynasties ascended to power. The best known of the three, the Samanid, extended its rule from Bukhara as far south as India and west as Iran. Although Arab Muslim intellectual life still was centered in Baghdad, Iranian Muslim scholarship, that is, Shia Islam, predominated in the Samanid areas at this time. By the mid-tenth century, the Samanid Dynasty had crumbled in the face of attacks from Turkish tribes to the north and from the Ghaznavids, a rising dynasty to the south.

Data as of 1997