The Imperial Coronation of 800 and Carolingian Diplomacy

The background to Charlemagne's coronation was a crisis in Rome: in 799, Pope Leo III was physically attacked, and he fled to the Frankish court, where Charlemagne mediated on his behalf. Charlemagne then traveled to Rome in 800 to resolve the papal crisis, and a Roman synod cleared Leo III of the charges against him through a purgatorial oath. On Christmas Day, 25 December 800, Leo III crowned Charlemagne "Imperator Romanorum" in the Basilica of St. Peter. Einhard's account claims Charlemagne was taken by surprise at the coronation, though this claim remains a matter of scholarly debate.