Don't sweat it. Originality is good, as far as it goes, but believe it or not it can be overdone. If you truly create a culture unlike anything that's ever existed before, your readers may find they have nothing to latch onto, nothing that is familiar to them, and that they have to learn absolutely everything about your universe.
That can be too much work, and you may lose them. Go right ahead and base on historical cultures all you want. Give your readers a familiar foundation with your unique twists on top of it, and your readers may find it easier to latch on and accept your world.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.