His reign was not long; and it was sufficiently occupied by the Roman and Armenian wars, and by the greatest of all his works, the reformation of religion.
The religious aspect of the insurrection which transferred the headship of Western Asia from the Parthians to the Persians, from Artabanus to Artaxerxes, has been already noticed; but we have now to trace, so far as we can, the steps by which the religious revolution was accomplished, and the faith of Zoroaster, or what was believed to be such, established as the religion of the State throughout the new empire.

Artaxerxes, himself (if we may believe Agathias) a Magus, was resolved from the first that, if his efforts to shake off the Parthian yoke succeeded, he would use his best endeavors to overthrow the Parthian idolatry and install in its stead the ancestral religion of the Persians.
This religion consisted of a combination of Dualism with a qualified creature-worship, and a special reverence for the elements, earth, air, water, and fire.

Zoroastrianism, in the earliest form which is historically known to us, postulated two independent and contending principles--a principle of good, Ahura-Mazda, and a principle of evil, Angro-Mainyus.

These beings, who were coeternal and coequal, were engaged in a perpetual struggle for supremacy; and the world was the battle-field wherein the strife was carried on.

Each had called into existence numerous inferior beings, through whose agency they waged their interminable conflict.