Holy Roman Empire. Of course most people are quick to claim that it wasn't Roman or an Empire thanks to the old Voltaire quote (which, dumbasses, in context wasn't intended to be factual but rhetorical). Although indeed unconventional, it was a massive power that dominated Europe for over a millennium, encompassing what are now Germany, Austria, Belgium, Luxembourg, the Netherlands, Czech Republic, Switzerland, Liechtenstein, much of Italy, and parts of France, Denmark, and Poland. It was unified by the idea of an alliance of Christiandom that didn't need the blessing of the Pope to perpetuate that. And indeed the Empire as it was known as contemporarily (the "holy roman" part only added by historians to differentiate it) secured Europe for 1000 years. Why is it that the Empire gets so little coverage in most folk's education growing up? Jew propaganda. The entire idea was that German lands were for German folks, Polish for Polish, etc. By being part of the empire everyone agreed to that. In exchange they also all agreed that European Christendom was for European Christians. Eschewing the problems that eventually felled the original Roman Empire and others they neither over stretched themselves nor invited anyone else in, and if you fucked with one member you fucked with them all. Kiked history lessons try to pass it off as unimportant because not a lot happened. What they mean is it was by and large a period of peace, prosperity, and pogroms.