In the summer of 1527, the university was removed to Jena, because the plague had broken out in Wittenberg. When Melanchthon had finished his first visitation tour, he continued to lecture in Jena, and wrote against the Anabaptists, who were also carrying on their sectarianism in various parts of Saxony. In the autumn of 1528, he made his second visitation tour into Thuringia, together with Myconius and Menius.
It is reasonable to suppose that the Pope could not have been satisfied with the great activity of the evangelical party, and the constantly increasing and noble spread of the gospel. He had but too many adherents in Germany, who were filled with the most violent rage against the Evangelical party. DUKE GEORGE of Saxony, who had been frequently attacked by Luther, especially breathed vengeance. He had in his service a counsellor, named OTTO VON PACK. It is a mystery to the present day, how this man came to reveal a pretended secret to the son-in-law of the Duke, the well-known Landgrave, Philip of Hesse, according to which the Catholic princes had formed a league against the evangelical states. He succeeded in presenting the matter in so plausible a manner, that Philip, who was already inclined to fight, believed it necessary to form a counter-league. Even the Elector John, who was otherwise more sober and calm, was of the same opinion. The Landgrave was not satisfied with mere words, but marched to the frontier with his troops; but the Elector was prudent enough to ask the opinions of his theologians, among whom Melanchthon was included.
Their advice was quite temperate. Although they were highly incensed at this Catholic league, they would hear nothing of an attack. How much Melanchthon was inclined to a scriptural peace, is shown in a letter addressed by him to the Elector on the 18th of May, 1528: "To have a good conscience, and to enjoy the friendship of God, is surely the best consolation in all afflictions. But if we should begin by seizing the sword, and commence a war with an evil conscience, we would have lost this consolation. Great sorrow and cares induce me to write this. God knows that I do not value my own life so highly, but I am only thinking how much dishonor might be brought upon the holy Gospel, should your Electoral Grace begin to war, without previously making use of all means and ways to preserve the peace, which indeed ought to be done." The Elector was of the same opinion, but the Landgrave stood prepared to fight. But when he wrote to his father-in-law, Duke George, he declared the whole matter to be "an unfounded lying report." Although the evangelical party could hardly believe this assertion, and perhaps had reason for it, they were, nevertheless, obliged to put an end to all further preparations.