A:
In biblical times, the Persians were followers of Zoroastrianism. This faith had arrived in Persia from what is now eastern Iran some two hundred years before the Babylonian Exile, probably originating in southern Russia over a thousand years earlier. Some scholars see Zoroastrian influences in post-Exilic Judaism.
islam
Islam (muslims)
They were polytheistic, with the principal god of the upper classes Ahura Mazda - the great light, this religion being codified by Zoroaster whose sect was Zorastrianism. Remnants of this religion still exist today in Persia, Tajikistan, Pakistan and in particular India where they are also known as Parsis (or Parsees).
Monotheistic, because the Persian religion was Zoroastrianism which is a monotheistic religion
At first, they treated them with fairness but much more crule as the empire went on.
No religion is called old or modern religion. God religions are revealed by God and remains as assigned and commanded by God. The main religion of Persians is Islam.
Zoroastrianism
Zoroastrianism or Mazdaism.
Most Persians today are Muslim, but before the advent of Islam in Persia, most Persians were Zoroastrians.
Persians are practicing the religion of Islam.
Jeid
Most Persians today are Muslim, but before the advent of Islam in Persia, most Persians were Zoroastrians.
ancient Persians
islam
Islam (muslims)
The most widely practiced religion in Ancient Persia is now known as Zoroastrianism. However, in the centuries after the Islamic conquest of Persia, most Persians converted to Islam (both by choice and from fear of violence). Islam (specifically Twelver Shiite Islam) is the dominant religion among ethnic Persians today.
Prior to the conversion to Islam, the predominant religion of Persia was Zoroastrianism.