During the first half of the 1st millennium CE, an empire arose in Persia that extended its power and influence to Mesopotamia in the east, Arabia in the south, the Caucasus Mountains in the north, and as far east as India. This empire, known alternatively as the Sasanian Empire or Sassanid Empire, was the last of three great dynasties in Persia - the Achaemenid and the Parthian being the first two dynasties - before the rise of Islam. In fact, many scholars consider the Sasanian Empire to be the last great empire of the ancient Near East because once it had been obliterated, Islam became the standard religion of the region, ushering in the Middle Ages.

Thanks to the Sasanians’ efforts with regard to religion, modern scholars know much more about Zoroastrianism than they would have if the religion continued to disseminate orally. Their efforts also protected Zoroastrian knowledge in later years after the dynasty was long gone and Islam became ascendant in Persia.

The Sasanians, like the Achaemenids and Parthians, also carried forth the Persian conflicts with the Hellenic world. Although the Achaemenids fought the Macedonian Greeks and the Parthians challenged the imperial Romans for control of Mesopotamia, the Sasanians faced Rome in its later stages of collapse and subsequently fought the revitalized Byzantine Empire. An examination of Sasanian chronology and culture reveals that it was a much more important dynasty and empire than most may think.

The Sasanians also had a profound global influence through one of the most idiosyncratic religions of the ancient Middle Eastern world: Manichaeism. Like Zoroastrianism, the Manichaean religion has a rich history, as seen in its interactions with early Christianity and its unparalleled emphasis on secrecy.