Papal influence, meanwhile, had been brought to bear on the Elector Frederick, to induce him not to take the part of Luther, and the chief agent chosen for working on the Elector and the Emperor Maximilian was the Papal legate, Cardinal Thomas Vio of Gäeta, called Caietan, who had made his appearance in Germany. The University of Wittenberg, on the other hand, interposed on behalf of their member, whose theology was popular there, and whose biblical lectures attracted crowds of enthusiastic hearers. He had just been joined at Wittenberg by his fellow-professor Philip Melancthon, then only twenty-one years old, but already in the first rank of Greek scholars, and the bond of friendship was now formed which lasted through their lives. The university claimed that Luther should at least be tried in Germany.

Luther expressed the same wish through Spalatin to his sovereign. He now also answered publicly the attack of Prierias upon his theses, and declared not only that a Council alone could represent the Church, but that even a decree of Council might err, and that an Act of the Church was no final evidence of the truth of a doctrine. Being threatened with excommunication, he preached a sermon on the subject, and showed how a Christian, even if under the ban of the Church, or excluded from outward communion with her, could still remain in true inward communion with Christ and His believers, and might then see in his excommunication the noblest merit of his own.

The Pope, meanwhile, had passed from his previous state of haughty complacency to one of violent haste. Already, on August 23, thus long before the sixty days had expired, he demanded the Elector to deliver up this 'child of the devil,' who boasted of his protection, to the legate, to bring away with him. This is clearly shown by two private briefs from the Pope, of August 23 and 25, the one addressed to the legate, the other to the head of all the Augustinian convents in Saxony, as distinguished from the Vicar of those congregations, Staupitz, who already was looked on with suspicion at Borne. These briefs instructed both men to hasten the arrest of the heretic; his adherents were to be secured with him, and every place where he was tolerated laid under the interdict. So unheard of seemed this conduct of the Pope, that Protestant historians would not believe in the genuineness of the briefs; but we shall soon see how Caietan himself refers to the one in his possession.

Other and general relations, interests, and movements of the ecclesiastical and political life of the German nation now began to exercise an influence, direct or indirect, upon the history of Luther and the development of the struggles of the Reformation, and even caused the Pope himself to moderate his conduct.

Whilst questions of the deepest kind about the means of salvation, and the grounds and rules of Christian truth, had been opened up for the first time by Luther during the contest about indulgences, the abuses, encroachments, and acts of tyranny committed by the Pope on the temporal domain of the Church, and closely affecting the political and social life of the people, had long been the subject of bitter complaints and vigorous remonstrances throughout Germany. These complaints and remonstrances had been raised by princes and states of the Empire, who would not be silenced by any theories or dogmas about the Divine authority and infallibility of the Pope, nor crushed by any mere sentence of excommunication. And in raising them they had made no question of the Divine right of the Papacy. Was it not natural that, in the indignation excited by their wrongs, they should turn to the man who had laid the axe to the root of the tree which bore such fruit, and at least consider the possibility of profiting by his work? Luther, on his part, showed at first a singularly small acquaintance with the circumstances of their complaints, and seemed hardly aware of the loud protests raised so long on this subject at the Diets. But with the question of indulgences the field of his experience broadened in this respect. The care he evinced in this matter for the care of souls and true Christian morality made him the ally of all those who were alarmed at the vast export of money to Rome, about which he had already said in his theses that the Christian sheep were being regularly fleeced.

In another respect, also, the ecclesiastical policy of the Papal see was closely interwoven with the political condition and history of Germany. If in theory the Pope claimed to control and confirm the decrees even of the civil power, in practice he at least attempted to assert and maintain an omnipresent influence. And with regard to Germany it was all-important to him that the Empire should not become so powerful as to endanger his authority in general and his territorial sovereignty in Italy. However loftily the Popes in their briefs proclaimed their immutable rights, derived from God, and their plenary power, and took care to let theologians and jurists advance such pretensions, they understood clearly enough in their practical conduct to adjust those relations to the rules of political or diplomatic necessity.

In the summer of 1518 a Diet was held at Augsburg, at which the Papal legate attended. The Pope was anxious to obtain its consent to the imposition of a heavy tax throughout the Empire, to be applied ostensibly for the war against the Turks, but alleged to be wanted in reality for entirely other objects. The Emperor Maximilian, now old and hastening to his end, was endeavouring to secure the succession of his grandson Charles, and Caietan's chief task was to exert his influence with Maximilian and the Elector Frederick to bring Luther into their disfavour. The Archbishop Albert, who had been hit so hard by Luther's attack on the traffic in indulgences, was solemnly proclaimed Cardinal by order of the Pope.

Of Maximilian it might fairly have been expected that, after his many experiences and contests with the Popes, he would at least protect Luther from the worst, however unlikely it might be that he should entertain the idea of effecting, by his help, a great reform in the National Church. He did indeed express his wish to Pfeffinger, a counsellor of the Elector, that his prince should take care of the monk, as his services might some day be wanted. But he supported the Pope in the matter of the tax, and hoped to gain him for his own political ends. He opposed Luther also in his attack on indulgences, on the ground that it endangered the Church, and that he was resolved to uphold the action taken by the Pope.

This demand for a tax, however, was received with the utmost disfavour both by the Diet and the Empire; and a long-cherished bitterness of feeling now found expression. An anonymous pamphlet was circulated, from the pen of one Fischer, a prebendary of Wiirzburg, which bluntly declared that the avaricious lords of Rome only wished to cheat the 'drunken Germans,' and that the real Turks were to be looked for in Italy. This pamphlet reached Wittenberg and fell into the hands of Luther, whom now for the first time we hear denouncing 'Roman cunning,' though he only charged the Pope himself with allowing his grasping Florentine relations to deceive him. The Diet seized the opportunity offered by this demand for a tax, to bring up a whole list of old grievances; the large sums drawn from German benefices by the Pope under the name of annates, or extorted under other pretexts; the illegal usurpation of ecclesiastical patronage in Germany, the constant infringement of concordats, and so on. The demand itself was refused, and in addition to this, an address was presented to the Diet from the bishop and clergy of Liege, inveighing against the lying, thieving, avaricious conduct of the Romish minions, in such sharp and violent tones that Luther, on reading it afterwards when printed, thought it only a hoax, and not really an episcopal remonstrance.

This was reason enough why Caietan, to avoid increasing the excitement, should not attempt to lay hands on the Wittenberg opponent of indulgences. The Elector Frederick, from whose hands Caietan would have to demand Luther, was one of the most powerful and personally respected princes of the Empire, and his influence was especially important in view of the election of a new Emperor. This prince went now in person to Caietan on Luther's behalf, and Caietan promised him, at the very time that the brief was on its way to him from Rome, that he would hear Luther at Augsburg, treat him with fatherly kindness, and let him depart in safety.