Zoroastrianism and it was Zoroastrianism and it was really Cyrus the Great by establishing the Persian Empire who really spreads Zoroastrianism and Zoroastrianism is based on their prophet Zarathustra and when Zarathustra lived is up for some debate. It might be as early as 1500 BCE. Some people say it might be even right before or even coincident with the life of Cyrus the Great and so there's some debate on when Zarathustra lived but it was a monotheistic religion following the one god of Ahura Mazda. Ahura Mazda and it was based on these ideas of good thoughts lead to good words and good deeds. Other big ideas of the Persian Empire is their system of governance. Because it was such a vast empire, they delegated the emperor, the Shahanshah, the king of kings, delegated authority to the regions. So each region, each satrapy had its governor called a satrap and as we see over time, some of these satraps got more power than maybe was intended and then eventually took over but this was a major empire in the history of the world.