The dimensions of history. It is my, probably sound, guess that all the major stuff we call history has a mystical element, in the sense of someone's experience sometime. Joan of Arc is just an obvious example. (May 30 is the date of her death, in 1431.) One interesting way this might happen is that people begin massive external building projects, under the energy involved and, most typically, misinterpreted (misinterpreted is an inside joke since ANY interpretation of a so-called mystical experience is a MISinterpretation.). The pyramids jump to mind, the expansion of Islamic culture, the crazy way western Europeans just decided, hey let's cross the mediterranean and attack those nice folks over there. (That thought started with the Crusades in mind.). Not that I have proof in my previous examples, I am speculating here. But it is plausible that we may owe, to someone's misinterpretation, indeed, perhaps an active turning away from a glimpsed reality, the major events in a high school history book. Only of course, if I am right, then so called historical causation is, the way it is currently written, utterly wide of the mark. Or perhaps, in the words of Jan Cox: "History is dreams."
And going back to misinterpretation being an inside joke, --- the reality behind that is why you could call, in the words of Jan Cox, "vertical expansion", a secret, --- meaning a secret you keep from yourself.