The Catholic Church claims Constantine “donated” his imperial regalia-scepter, crown, etc.-to the bishop of Rome in a document purportedly dating from his victory over Maxentius in AD 312. Constantine’s regalia thereby became the property of the Church, which returned the items to Constantine as a sort of ecclesiastical loan.
In effect, the Donation gave the Church the right to create and depose monarchs. The actual document is widely considered to be a forgery, but at the time it appeared (AD 753) it was a powerful justification for the deposition of Childeric III, the last Merovingian, for Pepin III, the first Carolingian. Citing authority from the Donation of Constantine, in 800 the Church crowned Charlemagne Holy Roman Emperor. In this way, the Church circumvented the pact it had made with Childeric’s ancestor, Clovis II.