On November 30, 1528, the Emperor summoned a Diet to meet at Spires on February 21 of the following year, in order that decisive and energetic measures should be taken—as recommended once more by the Pope—to secure the unity and sole supremacy of the Catholic Church. The chief subjects named for deliberation were, the armament against the Turks, and the innovations in matters of religion.
As regards the war against the Turks, Luther, who had previously let fall some occasional remarks about certain wholesome effects it would have in checking the designs of the Papacy, let his voice be heard, notwithstanding, in summoning the whole nation to do battle against the fearful and horrible enemy, whom they had hitherto suffered so shamefully to oppress them. Since the latter part of the summer of 1528 he had been engaged upon a pamphlet 'On the War against the Turks,' the publication of which was accidentally delayed till March, when he was busy with his Catechism.
In this pamphlet he spoke to his fellow-Germans, with the noblest fire and in the fulness of his strength, as a Christian, a citizen, and a patriot, and with a clearness and decision derived from convictions and principles of his own. He had no wish to preach a new crusade; for the sword had nothing to do with religion, but only with bodily and temporal things. But he exhorted and encouraged the authority, whom God had entrusted with temporal power, to take up the sword against the all-devouring enemy, with sure trust in God and certain confidence in his mission. By the 'authority' he meant the Emperor, in whom he recognised the head of Germany. He it was who must fight against the Turks; under his banner they must march, and upon that banner should be seen the command of God, which said 'Protect the righteous, but punish the wicked.' 'But,' asked Luther, 'how many are there who can read those words on the Emperor's banner, or who seriously believe in them?' He complained that neither Emperor nor princes properly believed that they were Emperor and princes, and therefore thought little about the protection they owed to their subjects. Further on he rebuked the princes for letting matters go on as if they had no concern in them, instead of advising and assisting the Emperor with all the means in their power. He knew well the pride of some of the princes, who would like to see the Emperor a nonentity and themselves the heroes and masters. Rebellion, he said, was punished in the case of the peasants; but if rebellion were punished also among princes and nobles, he fancied there would be very few of them left. He feared that the Turk would bring some such punishment upon them, and he prayed God to avert it. Finally, he bade them remember not to buckle on their armour too loosely, and underrate their enemies, as Germans were too prone to do. He warned them not to tempt God by inadequate preparation, and sacrifice the poor Germans at the shambles, nor as soon as the victory was won to 'sit down again and carouse until the hour of need returned.'
At Spires, however, the whole zeal of the imperial commissaries and of the Catholic Estates was directed, not against the common enemy of Germany and Christendom, but to the internal affairs of the Church. They succeeded in passing a resolution or article, declaring that those States which had held to the Edict of Worms should continue to impose its execution on their subjects; the other States should abstain at least from further innovations. The celebration of the mass was not to be obstructed, nor was anyone to be prevented from hearing it. The subjects of one State were never to be protected by another State against their own. By these means, not only was the Reformation prevented from spreading farther, but it was cut off at a blow in those places where it had already been in full swing. By the decision respecting the mass, room was given for attempts to reinstate it on Evangelical territory; by the other decision respecting the subjects of different States, power was given to the bishops of the German Empire to coerce, if they chose, the local clergy, as their subordinates. Further steps in the exercise of this power could easily be anticipated.
This resolution of the majority was answered on April 19 by the Evangelical party with a formal protest, from which they received the name their descendants still bear—Protestants. They insisted that the Imperial Recess unanimously agreed on at the first Diet of Spires in 1526 could only be altered by the unanimous consent of the States; and they declared 'that, even apart from that, in matters relating to the honour of God and the salvation of our souls, every man must stand alone before God and give account for himself.' In these matters, therefore, "they could not submit to the resolution of the majority."
The majority, however, as well as Ferdinand, the Emperor's brother and representative, refused to admit their right of opposition. The minority must prepare to submit to coercion and the exercise of force. Against this the Elector and Landgrave concluded, on April 22, a 'secret agreement' with the cities of Nüremberg, Strasburg, and Ulm. The Landgrave was eager that this alliance should be strengthened by the admission of Zurich and the other Evangelical towns in Switzerland. And a similar proposal was made to him by Zwingli, who, in connection with his ecclesiastical labours, was carrying on a bold and high policy, in striving to effect an alliance with the republic of Venice and the King of France against the Emperor, He certainly far overrated the importance of his town in the great affairs of the world, and placed a strangely naive confidence in the French monarch.
Luther, on the contrary, set his face as resolutely now as in the affair of Pack, against any appeal to the sword in support of the gospel. He would have his friends rely on God and not on the wit of man; and, with regard to the last Diet, he was quite content that God had not allowed their enemies to rage even more. He was willing even to trust to the Emperor for relief; the Evangelical party, he said, should represent to his Majesty how their sole concern was for the gospel and for the removal of abuses which no one could deny to exist; how, at the same time, they had resisted the iconoclasts and other riotous fanatics, nay, how the suppression of the Anabaptists and the peasants was pre-eminently due to them, and how they had been the first to bring to light and vindicate the rights and majesty of authority. A representation of this kind, he hoped, must surely have an influence on the Emperor. He flatly rejected any alliance with those,—namely, the Swiss,—who 'strive thus against God and the Sacrament;' such an alliance would disgrace the gospel and draw down their sins upon their heads. This opinion, in which the other Wittenberg theologians, and especially Melancthon, concurred, determined that of the Elector.
The Landgrave did his utmost to remove this obstacle to an alliance with the Swiss. He urged a personal conference between the rival theologians on the question of the Sacrament. Luther and Melancthon were strongly opposed to such a step, inasmuch as the course of the controversy hitherto had not revealed a single point which offered any hope of reconciliation or mutual approach. Luther reminded him how, ten years before, the Leipzig disputation served only to make bad worse. Intrigues, moreover, were apprehended from the other side, lest the Lutherans should be held up to odium as the enemies of unity and obstacles to an alliance, and the Landgrave be alienated from them. Melancthon, indeed, had brought with him from Spires, where he had been staying with Philip, a suspicion that the latter inclined to the Zwinglians, and was right in his conjecture at least so far, that their doctrine did not appear to him nearly so questionable as to the Wittenbergers. But the simple fear of consequences made Luther unwilling and unable to refuse the Landgrave's urgent invitation, backed as it was with the concurrence of the Elector. He wrote to him on June 23, declaring his readiness to 'render him this useless service with all diligence,' and only entreated him to consider once more whether it would do more good than harm. The conference was to take place at the Castle of Marburg on Michaelmas day (1529).
Luther's sentiments in the interval are expressed in a letter which he wrote on August 2 to a distant friend, the pastor Brismann at Eiga. 'Philip (Melancthon) and myself,' he says, 'after many refusals and much vain resistance, have been at length compelled to give our consent, because of the Landgrave's importunity; but I know not yet whether our going will come to anything. We have no hopes of any good result, but suspect artifice on all sides, that our enemies may be able to boast of having gained the victory…. I am pretty well in body, but inwardly weak, suffering like Peter from want of faith; but the prayers of my brethren support me…. That youth of Hesse is restless, and boiling over with projects…. Thus everywhere we are threatened with more danger from our own people than from our enemies. Satan rests not, in his bloodthirstiness, from the work of murder and bloodshed.'
In the same letter Luther tells of the panic caused by a new pestilence—the Sweating Sickness—which had appeared in Germany and at Wittenberg itself. It was a plague, known already many years before, which used to attack its victims with fever, sweat, thirst, intense pain and exhaustion, and snatch them off with fearful rapidity. Luther knew well the danger of it when once it actually appeared. But he watched without terror the supposed symptoms of its appearance at Wittenberg, and remarked that the sickness there was mainly caused by fright. On the 27th he told another friend how the night before he had awoke bathed in sweat, and tormented with anxious thoughts, so much so, that had he given way to them he might very likely have fallen ill like so many others. He named also several of his acquaintances, whom he had driven out of bed, when they lay there fancying themselves ill, and who were now laughing at their own fancies.