These depredations, or these schemes of conquest, were not needed to arouse the fierce and passionate hostility of the pope to the all-absorbing Lombard. So long as there had been three great powers in Italy there had been an equilibrium of a certain kind between them. In fact, the pope had more than once invoked the help of the Lombard, “unspeakable” as he called him, against his “most Christian” sovereign in Constantinople, when the latter pressed him too hard. But now the pope and the Lombard king stood face to face with no other rival to their greatness, and each of them probably felt, dimly but certainly, that it would be a duel to the death between them. It was probably in the year 752, some months after the conquest of Ravenna, and when the hostile intentions of King Aistulf against Rome had been sufficiently indicated, that Pope Stephen II. sent a secret message by a pilgrim who had visited Rome, imploring the King of the Franks to give him a formal invitation to his court. In the spring of 753 the envoys of Pippin brought the desired invitation, and a letter, in which there was probably some promise of protection against the Lombards. Just about the same time a messenger, the _silentiarius_[28] John, arrived from the Emperor Constantine V., desiring the pope to repair to the court of Pavia and solicit King Aistulf to grant the restoration of Ravenna to the empire. The pope had sent more than one urgent message to the emperor imploring his protection, and this futile commission was the only reply. The form of the despatch showed that the emperor still regarded the pope as his subject, but its substance was certainly some justification to Stephen for that transfer of his allegiance from Constantine to Pippin, which had now begun to present itself to his mind as a possible way of escape from his difficulties. In itself the Imperial Commission was not unwelcome, since it necessitated a safe conduct from Aistulf for the journey to Pavia.