Luther himself wavered.

He attacked the sacrifice of the mass, in which he saw a "good work" repugnant to faith, and a great practical abuse, as in the endowed masses for souls, but he finally decided on the question of the real presence that the words "this is my body" were "too strong for him" and meant just what they said.
After a preliminary skirmish with Carlstadt, resulting in the latter's banishment from Saxony, there was a long and bitter war of pens between Wittenberg and the Swiss Reformers.

Once the battle was joined it was sure to be acrimonious because of the self-consciousness of each side.
Luther always assumed that he had a monopoly of truth, and that those who proposed different views were infringing his copyright, so to speak.

"Zwingli, Carlstadt and Oecolampadius would never have known Christ's gospel rightly," he {109} opined, "had not Luther written of it first." He soon compared them to Absalom rebelling against his father David, and to Judas betraying his Master.

Zwingli on his side was almost equally sure that he had discovered the truth independently of Luther, and, while expressing approbation of his work, refused to be called by his name.