Late in 1521, Karlstadt and Zwilling started to drive the Wittenberg reformation in a radical direction. Stirring up iconoclasm and riots, Karlstadt took to walking around Wittenberg dressed as a peasant and officiating at mass in a plain robe. Then three individuals arrived, the Zwickau Prophets, who believed in the continuing direct leading of the Holy Spirit and thereby neglected the crucial centrality of the Word and the inseparability of Word and Spirit.
Wittenberg looked set to descend into chaos. Luther returned incognito in December 1521 and, while pleased at the strides the reforms were making, he was deeply disturbed by the chaotic atmosphere and the iconoclasm. Then, in early 1522, the Elector recalled him to the town permanently.
This was the moment Luther was most vulnerable. Like Will Kane in High Noon, he was now totally alone. His theological allies were either too timid or had gone over to the charismatic lunacy of the men from Zwickau. The knights were conspicuous by their absence. And the Elector was waiting to see what would happen: he knew that if the reformation in Wittenberg could not be brought under control, he risked invasion from the Emperor; if Luther failed, Frederick would have to reimpose the old ways. Luther had no decisive allies. It was all down to him.
Carl Trueman, Luther, Beer and 1522.