The "Christian Caesar"
"He became Western Europe's ‘Christian Caesar'—a Roman Emperor born of a Germanic race. The West once again had an emperor, and his coronation was to become the central event of the Middle Ages.
"He was proclaimed Rex Pater Europae (King Father of Europe) and espoused the ideal of a unified Christian Empire—albeit Christianized at sword point—in close alliance with the Pope. The fact that Charlemagne received his crown from the Pope was seen by the populace as equal to a divine bestowal. It confirmed the perception that the imperial crown was a papal gift, and that the kingdoms of this earth belonged to the Bishop of Rome; they were his to give and his to take away...
"The two had become joint sovereigns on earth, in a Holy Roman Empire which was the political foundation of the Middle Ages. Throughout this era, the memory of the once-great Roman Empire lived as a vital tradition in the hearts of many Europeans. The entire future of the Continent was bound up in this coronation, and the alliance between the papacy and Germany has been of great significance ever since" (Adrian Hilton, The Principality and Power of Europe, 1997, p. 26). WNP