In the early part of the eighth century Leo Isauricus, one of the successors of Constantine on the imperial throne, not content with his civil authority, endeavored, like Henry VIII., to usurp spiritual jurisdiction, and, like the same English monarch, sought to rob the people of their time-honored sacred traditions. A civil ruler dabbling in religion is as reprehensible as a clergyman dabbling in politics. Both render themselves odious as well as ridiculous. The Emperor commanded all paintings of our Savior and His saints to be removed from the churches on the assumption that such an exhibition was an act of idolatry. Pope Gregory II. wrote to the Emperor an energetic remonstrance, reminding him that "dogmas of faith are to be interpreted by the Pontiffs of the Church and not by emperors," and begging him to spare the sacred paintings. But the Pope's remonstrance and entreaties were in vain. This conduct of the Emperor tended to widen still more the breach between himself and the Roman people.
Soon after an event occurred which abolished forever the authority of the Byzantine Emperors in Italy, and established on a sure and lasting basis the temporal sovereignty of the Popes.
In 754 Astolphus, King of the Lombards, invaded Italy, captured some Italian cities and threatened to advance on Rome.
Pope Stephen III.,(183) who then ruled the Church, sent an urgent appeal to the Emperor Constantine Copronymus, successor of Leo the Isaurian, imploring him to come to the relief of Rome and his Italian provinces. The Emperor manifested his usual apathy and indifference and received the message with coldness and neglect.
In this emergency Stephen, who sees that no time is to be lost, crosses the Alps in person, approaches Pepin, King of France, and begs that powerful monarch to protect the Italian people, who were utterly abandoned by those that ought to be their defenders. The pious King, after paying his homage to the Pope, sets out for Italy with his army, defeats the invading Lombards and places the Pope at the head of the conquered provinces.
Charlemagne, the successor of Pepin, not only confirms the grant of his father, but increases the temporal domain of the Pope by donating him some additional provinces.