Another mistake: Charlemagne was technically a successor to Constantine VI who was the emperor of the Eastern Roman/Byzantine Empire. After Empress Irene (alleg

Another mistake: Charlemagne was technically a successor to Constantine VI who was the emperor of the Eastern Roman/Byzantine Empire. After Empress Irene (allegedly) murdered her son and ascended to the throne on her own right the pope in the west did no recognize her (also because she was a woman) and crowned Charlemagne instead. However unlike most other usurpers throughout Roman history he did not march to Constantinople to depose Irene and therefore both empires coexisted for the 700 years or so. HRE (it was just called the Roman Empire, the word holy was only added in the high middle ages) was not a successor to the Western Roman Empire. That wouldn't really make any sense, since the Roman had already reconquered Italy (and the lost most of it) after the Western Empire had fallen (Rome itself was still formally a part of the (eastern)Empire at the time of Charlemagne.