I was left wondering this question, could it be possible that the Sith were based of a mystical secret society with esoteric practices? I thought this may be an interesting discussion.
The Sith do seem to be space Illuminati. I'd bet GL was inspired by false flag atttacks combined with the Illuminati.
I think GL was influenced is some form by the Persian Empire's military magi order. They are similarly as they were known as sorcerer warriors who were feared and brutal in their tactics. GL is really the only one who can answer that and I don't think he ever has answered that question.
Lucas has said that the Jedi were partially based off of the Samurai, as he was a fan of Akira Kurosawa films. Ninjas are often said to be the adversaries of the Samurai, since they use different tactics from the Samurai. They have different values and methodologies that put them at opposite ends. So I think there is a possible connection there. The Persian military force might be part of his influence.
