and early Ummayads, the administrative system of the late Sasanian period was largely retained: a pyramidal system where each quarter of the state was divided into provinces, the provinces into districts, and the districts into sub-districts. Provinces were called ustan (Middle Persian ostan), and the districts shahrs, centered upon a district capital known as a shahristan. The subdistricts were called tasok in Middle Persian, which was adopted into Arabic as tassuj (plural tasasij). Religion Zoroastrians were made to pay an extra tax called jizya, or be killed, enslaved or imprisoned. Those paying jizya were subjected to insults and humiliation by the tax collectors. Zoroastrians who were captured as slaves in wars were given their freedom if they converted to Islam. While giving freedom of choice, the Arab conquerors designated privileges for those who converted to Islam. The conversion process was slow and uncompleted, stretching over many centuries, with a majority of Persians still following Zoroastrianism at the turn of the millennium. Muslim leaders in their effort to win converts encouraged attendance at Muslim prayer with promises of money and allowed the Quran to be recited in Persian instead of Arabic so that it would be intelligible to all. Islam was readily accepted by Zoroastrians who were employed in industrial and artisan positions because, according to Zoroastrian dogma, such occupations that involved defiling fire made them impure. Moreover, Muslim missionaries did not encounter difficulty in explaining Islamic tenets to Zoroastrians, as there were many similarities between the faiths. According to Thomas Walker Arnold, the Persian would meet Ahura Mazda and Ahriman under the names of Allah and Iblis. In Afghanistan, Islam was spread due to Umayyad missionary efforts particularly under the reign of Hisham ibn Abd al-Malik and Umar ibn Abd al-Aziz. There were also large and thriving Christian and Jewish communities, along with smaller numbers of Buddhists and other groups. The population moved slowly and steadily toward Islam. The nobility and citizens converted first. Islam spread more slowly among the peasantry and the dihqans, or landed gentry. By the late 10th century, the majority of the Persians had become Muslim. Until the 15th century, most Persian Muslims were Sunni Muslims, though with rise of Safavids in early 16th century and their forced conversion of Sunnis lead to rise of Shi'a Muslim faith in Iran. Language of Persia During the Rashidun Caliphate, the official language of Persia (including Mesopotamia) remained Middle