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I remember a story that deals with humans on Earth having some sort of long-term, long-distance interaction (perhaps war/conflict, but I think they were benevolent in some way; but I can't remember) with aliens, but over the course of those years or decades, no human ever saw one of the aliens. I remember the end being sort of a twist ending:
The story ends with the aliens landing on Earth and when the first one disembarks from their ship, we see they look a whole lot like the traditional image of a red devil with horns and a tail. They stayed hidden for so long because they were aware of the iconic devil image and didn't want us to associate them with the devil.
I don't know if this was a short story or novel. It may have been part of a collection of books a friend loaned me during the early to mid 1990's to broaden my SF/F perspectives; he included a lot of military fiction and some fantasy, both of which I hadn't read much. I've tried searching online using key terms but I have been unable to identify the story.