Tauler became the most powerful preacher of his day. He influenced many people in the towns and villages along the Rhine River. His converts did not leave the Roman Catholic Church. Instead, they formed prayer groups that sought spiritual union with God. Martin Luther said that reading Tauler’s sermons in later years affected him deeply.17 EVANGELIZATION BY RULERS Conversion by force was the rule rather than the exception in much of medieval Europe. Actions like that of King Bogoris were quite common.