Full Idea
It was only sometime around the sixth century BC, during the period when the Israelites returned to Jerusalem, that the idea that there is only one God emerged in Jewish religion.
Gist of Idea
Judaism only became monotheistic around 550 BCE
Source
John Gray (Seven Types of Atheism [2018], Intro)
Book Reference
Gray,John: 'Seven Types of Atheism' [Penguin 2019], p.5
A Reaction
There seems to be a parallel move among the Greeks to elevate Zeus to special status.