The Empire was not intended to supersede this system of royal government; kings no less than emperors were regarded as holding a definite rank and office in the Christian commonwealth. No traditions of imperial bureaucracy, except in a debased and orientalised form, were accessible to Charles the Great. In Gaul and Italy he had subjects who lived under a corrupt and mutilated Roman Law; but he was unacquainted with the scientific principles of the great jurists whose writings were the highest achievements of the Roman genius. To the best minds of the eighth century the Roman Empire appeared, not as to an Athaulf or a Theodoric, a masterpiece of human statesmanship, but rather a divine institution, providentially created before the birth of Christ to school the nations for the universal domination of His Church. The model of the Carolingian Emperors was not Augustus but Constantine the Great, the Most Christian ruler who made it his first business to protect the Church against heretic and heathen, to endow her with riches, to enforce her legislation. However his relation to the Pope might be conceived, the Emperor held his office as the first servant of the Church. What then were his practical duties? According to some he was pledged to restore the material unity of Christendom and to subdue all heathen peoples. This childlike ideal of his office no emperor could put into practice. Charles the Great waged no important wars after his coronation; he did not scruple to make peace with the Eastern Empire or even to exchange courtesies with Haroun al Rashid, the Caliph of Bagdad. He held, and the sanest of his counsellors agreed, that his first duty was to protect, unite and reform the societies over which the Church already exercised a nominal dominion. To conquer other Christian rulers was no more to be expected of him than that he should surrender his own royal prerogative; though it was desirable that they should do homage to him as the earthly representative of spiritual unity. Within his own realms the imperial office was to make a difference in the spirit rather than the forms of government. The Empire raised to a higher power the dignity and the responsibilities which belonged to him as a king. He conceived himself bound to provide more carefully than ever for the maintenance of ecclesiastical and the betterment of secular law. His subjects were to realise that through their allegiance to him they were God's subjects, bound to observe the law of God as a part of the law of the Empire; he on his side was to be, to the best of his power, a moral censor, an educator, a religious missionary, a protector of the clergy, a defender of the faith.