During the same Christmas season in Rome (in fact, only a few days after Charlemagne had officiated over the exoneration of the pope) an event took place which was to have profound repercussions on the history of the Christian Church – Charlemagne was declared the Roman emperor.
Since the fall of Rome to the barbarians in 476, the title of emperor of Rome, then shared by an Eastern and a Western emperor, had gone into the hands of the rulers of the Eastern empire, even though Byzantine culture was more Greek than Roman. What Pope Leo did was restore the dual nature of the imperial rule. His gesture had long intrigued historians because of its variety of interpretations.
In the company of his counts, Charlemagne entered Saint Peter’s for the Christmas ceremony wearing a Roman tunic and no crown. Leo welcomed him and led the king to the altar, where Charlemagne knelt to pray. After some time the king rose, and as he turned to the congregation, the pope placed a gold crown on his head, proclaiming Charlemagne “Charles the Augustus, crowned by God, the Great and Peaceful Emperor of the Romans.”
At first glance, Charlemagne’s coronation as emperor of Rome was a goal he had long set his sights on. Since 744, Italy had been in his effective control, and from that time he had expanded his kingdom to include much of the former Western empire. To be acknowledged emperor must have seemed Charlemagne’s due.
The one documented explanation extant, the Annales Laureshamensis, confirms this view. “Since the Byzantines poorly tolerated government by a woman (the Empress Irene), it seemed opportune for Pope Leo, with the backing of the church fathers assembled in Rome and all Christendom, to create Charles, the king of the Franks, emperor, since he held Rome, home of all the Caesars, as well as other parts of Italy, Germany and Gaul.”