I have been reading a lot about the early foundations of Zoroastrianism in Persia and its evolution in antiquity. I know that Darius I justified his reign as himself being the secular ruler under Ahuramazda.
"By the grace of Ahuramazda am I king; Ahuramazda has granted me the kingdom."
Is this a case of divine right to rule, akin to how catholic leaders were merely a secular authority and not necessarily divine themselves? Or is this a case where he is essentially claiming to be Ahuramazda incarnate, like a God-King?
Additional question:
Did the Sumerians, Babylonians, Assyrians, etc. of Mesopotamia mark their kingships in a similar light of being granted their ability under a divine presence or did they legitimately imagine themselves Gods?
I have written at length on the Great King's religious role: https://old.reddit.com/r/AskHistorians/comments/a0cqhp/what_role_did_the_persian_emperor_play_in/eawirps/
Essentially, Darius' ideological assertions revolve around him being divinely inspired to act with perfect righteousness, granting him a claim to xšaça (kingship, princely power). My preferred comparison is with the Chinese Mandate of Heaven - the monarch is exalted above mortals to act as an intermediary between the gods and men.