Leo III was elected pope in Rome and, unlike his predecessor Hadrian I, quickly leaned on Charlemagne’s authority by recognizing him as patricius Romanorum (protector of Rome), setting the stage for tighter Carolingian–papal cooperation.
During a public procession in Rome, Leo III was assaulted by opponents associated with the previous papal regime, triggering a crisis that would draw Charlemagne directly into Roman ecclesiastical politics.
After fleeing Rome, Leo III met Charlemagne at Paderborn in the Frankish realm. The encounter cemented Leo’s reliance on Frankish protection and became a key prelude to the imperial coronation the following year.
Charlemagne entered Rome to resolve the conflict around Leo III and the accusations against him, asserting Carolingian authority as protector and arbiter in the city’s crisis.
A council assembled in Rome to hear parties for and against Leo III. Bishops maintained they could not judge the pope, underscoring the political-ecclesiastical impasse that Leo sought to end by a public oath.
Leo III publicly swore an oath of purgation to dispel accusations and restore his standing. This act, paired with Charlemagne’s backing, neutralized the immediate Roman opposition and cleared the way for the Christmas ceremonies.
During Christmas Mass at Old St. Peter’s, Pope Leo III crowned Charlemagne Emperor of the Romans. The coronation transformed the Frankish–papal alliance into an imperial framework and became a foundational episode for later medieval debates over imperial and papal authority.
After the coronation, Charlemagne staged an imperial court assembly at Aachen, consolidating governance and projecting the new imperial status into the administrative heart of the Carolingian realm.
After prolonged conflict and negotiation, Emperor Michael I in Constantinople recognized Charlemagne’s imperial title (as emperor, not “emperor of the Romans”), highlighting the continuing diplomatic fallout of the 800 coronation and the rivalry with Byzantium it intensified.
Late in his reign, Charlemagne crowned his son Louis (later Louis the Pious) as co-emperor, helping ensure dynastic continuity for the imperial title created through the 800 coronation.
Charlemagne died at Aachen, ending the reign of the first western emperor crowned in Rome since antiquity. His death raised immediate questions about how imperial authority would persist and how it would relate to papal power under his successors.
Leo III died in Rome after a pontificate defined by dependence on Carolingian support and by the imperial coronation of 800, a precedent that shaped later papal–imperial relations.
Pope Stephen IV crowned Louis the Pious at Reims, reaffirming the importance of papal participation in imperial legitimacy and extending the coronation model established with Charlemagne.
Louis the Pious and Pope Paschal I reached the Pactum Hludowicianum (also called Ludovicianum), setting terms for governance in central Italy and the relationship between the Papal States and the Carolingian Empire—an important attempt to formalize the post-800 balance of power.
Paschal I became pope immediately after Stephen IV’s death. His pontificate would be deeply concerned with managing relations between the papacy and the Carolingian imperial government.
The Coronation of Charlemagne and Papal Relations (799–822)
