‘‘We, who are the spiritual Israel’: thus spoke the imperious voice attributed to Charlemagne, the king of the Franks, in a massive theological treatise, the Opus Caroli, fulminating against the (as it saw them) heretical rulers of Byzantium. Imperious, and perhaps even proto-imperial, for within less than a decade of those words being written Charlemagne had been crowned emperor in Rome. The Opus Caroli systematically attacked the acts of the second council of Nicaea (787) as having embraced the worship of images and condemned its convenors, the Empress Irene and her son Constantine VI, as unworthy of their position, claiming that their arrogance constituted blasphemy, their practices idolatry, and that their empire was the spiritual descendant of pagan Babylon. Unsurprisingly then, recent studies of the Opus Caroli (previously known as the Libri Carolini) have presented it as the ideological preparation for the transformation of the kingdom of the Franks into an empire, seeking to replace the Greek empire with the ‘new Israel’ of the Franks.