Caliphate
The Umayyad Caliphate emerged as the rulers of the Islamic world. Although they maintained the Sasanians' administrative practices, the Umayyads considered Islam as primarily an Arab religion and were wary of Persian culture. They enforced use of the Arabic language in Persia, leading to the demise of the Middle Persian or Pahlavi alphabet in favor of the new Arabic/Persian alphabet in use to this day. They attempted to assimilate Persians as they had "Arabized" and assimilated the Egyptians and the Assyrians, but with much less success.