The emperor Maximilian was equally solicitous with the pope about putting a stop to the propagation of Luther's opinions in Saxony; troublesome both to the church and empire. Maximilian, therefore, applied to Leo, in a letter dated August 5, 1518, and begged him to forbid, by his authority, these useless, rash, and dangerous disputes; assuring him also, that he would strictly execute in the empire whatever his holiness should enjoin. In the meantime Luther, as soon an he understood what was transacting about him at Rome, used all imaginable means to prevent his being carried thither, and to obtain a hearing of his cause in Germany. The elector was also against Luther's going to Rome, and desired of cardinal Cajetan, that he might be heard before him, as the pope's legate in Germany. Upon these addresses, the pope consented that the cause should be tried before cardinal Cajetan, to whom he had given power to decide it. Luther, therefore, set off immediately for Augsburg, and carried with him letters from the elector. He arrived here in October, 1518, and, upon an assurance of his safety, was admitted into the cardinal's presence. But Luther was soon convinced that he had more to fear from the cardinal's power, than from disputations of any kind; and, therefore, apprehensive of being seized, if he did not submit, withdrew from Augsburg upon the 20th. But, before his departure, he published a formal appeal to the pope, and finding himself protected by the elector, continued to teach the same doctrines at Wittemberg, and sent a challenge to all the inquisitors to come and dispute with him.
As to Luther, Miltitius, the pope's chamberlain, had orders to require the elector to oblige him to retract, or to deny him his protection; but things were not now to be carried with so high a hand, Luther's credit being too firmly established. Besides, the emperor Maximilian happened to die upon the 12th of this month, whose death greatly altered the face of affairs, and made the elector more able to determine Luther's fate. Miltitius thought it best, therefore, to try what could be done by fair and gentle means, and to that end came to some conference with Luther. During all these treaties, the doctrine of Luther spread, and prevailed greatly; and he himself received great encouragement at home and abroad. The Bohemians about this time sent him a book of the celebrated John Huss, who had fallen a martyr in the work of reformation; and also letters, in which they exhorted him to constancy and perseverance, owning, that the divinity which he taught was the pure, sound, and orthodox divinity. Many great and learned men had joined themselves to him. In 1519, he had a famous dispute at Leipsic with John Eccius. But this dispute ended at length like all others, the parties not the least nearer in opinion, but more to enmity with each other's persons. About the end of this year, Luther published a book, in which he contended for the communion being celebrated in both kinds; which was condemned by the bishop of Misnia, January 24, 1520. While Luther was labouring to excuse himself to the new emperor and the bishops of Germany, Eccius had gone to Rome, to solicit his condemnation; which, it may easily be conceived, was now become not difficult to be attained. Indeed the continual importunities of Luther's adversaries with Leo, caused him at length to publish a formal condemnation of him, and he did so accordingly, in a bull, dated June 15, 1520; this was carried into Germany, and published there by Eccius, who had solicited it at Rome; and who, together with Jerom Alexander, a person eminent for his learning and eloquence, was entrusted by the pope with the execution of it. In the meantime, Charles V. of Spain, after he had set things to rights in the Low Countries, went into Germany, and was crowned emperor, October the 21st, at Aix-la-Chapelle. The diet of Worms was held in the beginning of 1521; which ended at length in this single and peremptory declaration of Luther, that "unless he was convinced by texts of scripture or evident reason (for he did not think himself obliged to submit to the pope or his councils,) he neither could nor would retract any thing, because it was not lawful for him to act against his conscience." Before the diet of Worms was dissolved, Charles V. caused an edict to be drawn up, which was dated the 8th of May, and decreed that Martin Luther be, agreeably to the sentence of the pope, henceforward looked upon as a member separated from the church, a schismatic, and an obstinate and notorious heretic. While the bull of Leo X. executed by Charles V. was thundering throughout the empire, Luther was safely shut up in the castle of Wittemberg; but weary at length of his retirement, he appeared publickly again at Wittemberg, March 6, 1522, after he had been absent about ten months. Luther now made open war with the pope and bishops; and, that he might make the people despise their authority as much as possible, he wrote one book against the pope's bull, and another against the order falsely called "the order of bishops." He published also, a translation of the "New Testament" in the German tongue, which was afterward corrected by himself and Melancthon. Affairs were now in great confusion in Germany; and they were not less so in Italy, for a quarrel arose between the pope and the emperor, during which Rome was twice taken, and the pope imprisoned. While the princes were thus employed in quarrelling with each other, Luther persisted in carrying on the work of the reformation, as well by opposing the papists, as by combating the Anabaptists and other fanatical sects; which, having taken the advantage of his contest with the church of Rome, had sprung up and established themselves in several places.