• There were still many other Councils from Constantine to Charlemagne, although these remain the main ones, in which the Princes showed themselves submissive and faithful to the Church. Especially Justinian after the fifth Council of 120 bishops (…). In fact, this is evident from the laws he made in favor of the ecclesiastical state. And also from the letter he sent throughout the empire after the celebration of the Council of Constantinople, in which he declared to submit to the institutions of the Church, ordering the people to obey her in everything, also reiterating the resolutions of the four Councils that we have recalled and reconfirming them, placing its sanctions and laws at the service of ecclesiastical institutions, especially regarding usury and marriage, around which all of life is based.
• This Council was held against Theodore and his followers in Constantinople, who affirmed that the Word of God was distinct from Christ, and they also denied Blessed Mary. The sixth, Then, it was celebrated in the aforementioned imperial city with the patronage of Constantine IV; they participated 150 bishops, at the request of Pope Agathon against (those) who maintained that there was only one operation and one will in Christ, according to the heresy of Eutyches. In this council Constantine, who lived 150 years after Justinian, he greatly promoted faith, destroying the Monothelite heretics, that his father and grandfather had favored, and had the churches destroyed by them restored.
• The facts mentioned are sufficient to demonstrate that the Emperors of Constantinople were protectors and active defenders of the Church of Rome until the time of Charlemagne. At that time, the Church being oppressed by the Lombards, and since the empire of Constantinople did not bring help, maybe because he couldn't, since his power had diminished, the Roman Pontiff called the King of the Franks to his defense against those barbarians. First Pope Stephen and his successor Zechariah called Pepin against Astolfo King of the Lombards; then Hadrian and Leo called Charlemagne against Astolfo's son Desiderio. After he was taken out of the way and defeated together with his people, because of such a great benefit, Adriano, celebrated in Rome a Council of 150 bishops and venerable abbots, transferred the Empire from the Greeks to the Germans in the person of the Magnificent Prince Charles; and in this episode we see with sufficient clarity how imperial power depends on the judgment of the Pope. Indeed, until the Emperors of Constantinople defended the Church of Rome, as Justinian did through Belisarius against the Goths, and Maurice against the Lombards, the Church favored these emperors. After they failed, as in the time of Emperor Michael, a contemporary of Charlemagne, he provided himself with another Emperor for his defense.
From Saint Thomas Aquinas, Of the government of the princes to the king of Cyprus, Non-negotiable principles on society and politics, Chapter XVIII of Book III: The two subsequent ecumenical councils and the reasons why the empire was transferred from the Greeks to

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