Even before the Peasants' War broke out, the proceedings of the fanatics had begun to hamper and disturb his labours in the field of reformation, and had prepared for him much pain and tribulation. He had to grow distrustful of so many whom he had regarded as brothers, and of their manner of proclaiming the Word of God, Whom they pretended to serve. He already heard of men among them, who not only rejected infant baptism, and openly attacked his own, no less than the Catholic doctrine of the Sacrament, but who impugned the universal belief of Christendom in the Triune God and the Divinity of the Saviour. Early in 1525 news reached him of such a man at Nüremberg, John Denk, the Rector of the school there, who was expelled on that account by the magistrates. Luther's own doctrine of the presence of Christ's Body in the Lord's Supper, which he had previously to defend against Carlstadt, his former colleague and fellow-combatant, now found a far more formidable opponent in the Zurich Reformer, Ulrich Zwingli. The latter, in a letter of November 16, 1524, to Alber, a preacher at Reutlingen, had already disputed the Real Presence, by interpreting the words 'This _is_ my body' to mean 'This _signifies_ my body.' In March 1525 he made known this interpretation to the world by publishing his letter, together with a pamphlet 'On the True and False Religion.' He was joined at Basle by Oecolampadius, whom Luther had welcomed formerly as a fellow-labourer, and who published his own interpretation of the words of Christ. Butzer and Capito, the evangelical preachers at Strasburg, inclined to the same view, which threatened to spread rapidly over the South of Germany. The opposition now encountered by Luther was far more dangerous for his teaching than the theories and agitations of a Carlstadt, since whatever judgment may be formed about its merits, it proceeded at any rate from men of far more thoughtful minds, more solid theological acquirements, and more honest reverence for the Word of God. Herewith then began that division of opinion among the ranks of the Evangelical Reformers, which served more than anything else to retard the fresh and vigorous progress of the Reformation, and infected even Luther's spirit with the bitterness of the controversy it entailed.