The Sasanian Empire was the last Persian imperial dynasty before the Muslim conquest, considered a peak of ancient Iranian civilization. Founded by Ardashir I in 224 AD, it revived Zoroastrianism and became the arch-rival of the Roman (and later Byzantine) Empire for over 400 years. The empire reached its zenith under Khosrow I and Khosrow II, extending from the Levant to India. Its sophisticated culture, art, and administration deeply influenced Islamic civilization. However, exhausted by long wars with Byzantium, it ultimately fell to the Rashidun Caliphate in 651 AD.