In 1520 Martin Luther dedicated his treatise "On the Freedom of the Christian Man" to his friend Hermann Muehlpfort, the Lord Mayor of Zwickau. The Anabaptist movement of 1525 began at Zwickau under the inspiration of the "Zwickau prophets". After Wittenberg, it became the first city in Europe to join the Lutheran Reformation. The late Gothic Gewandhaus (cloth merchants' hall), was built in 1522–24 and is now converted into a theatre. The city was seriously damaged during the Thirty Years' War.