What was the Sassanian Empire's role in facilitating the spread of universal religions and the development of common cultures in Afro-Eurasia. How...

The Sassanian Empire was the last Persian Empire before the rise of Islam. In geography, language, and cultural traditions, it exhibited significant continuities with the earlier Persian imperial dynasties, including the Achaemenid Empire (550–330 BC) and Parthian Empire (247 BC–224 AD). It maintained their traditions of highly centralized authority, elaborate bureaucracy, legalism (including a strong emphasis on fairness and consistent justice), and divinization of the king.

The Sassanid Empire lasted from 224 AD to 651 AD, and...

The Sassanian Empire was the last Persian Empire before the rise of Islam. In geography, language, and cultural traditions, it exhibited significant continuities with the earlier Persian imperial dynasties, including the Achaemenid Empire (550–330 BC) and Parthian Empire (247 BC–224 AD). It maintained their traditions of highly centralized authority, elaborate bureaucracy, legalism (including a strong emphasis on fairness and consistent justice), and divinization of the king.

The Sassanid Empire lasted from 224 AD to 651 AD, and was located between the Roman Empire to the west and India to the east. Being at a crossroads of major east-west and north-south trade routes it was also a center from which religions were disseminated.

The official religion of the Sassanid Empire was Zoroastrianism, a religion that dominated the region from approximately 600 BC to 650 AD. The major sacred text of the religion, the Avesta, was first compiled in this period from earlier oral traditions. Despite having a strong state religion, the Sassanid Empire offered more religious freedom that the Roman Empire to the west and substantial communities of both Platonists and Christian heretics fleeing persecution in the west settled in the Sassanid Empire. Of particular importance were the Nestorian Christians, whose form of Syriac Christianity was supported by the Sassanids as a way of ensuring the loyalty of Christian subjects in opposition to the Nicene Christianity of the Roman Empire. Thus the early Christian missions to the east, moving along the Silk Road, including India and China, were Nestorian, emanating from the Sassanid Empire. 

Zoroastrian tradition also influenced the theology of the Abrahamic religions, especially Islam as it took root in Persia.