The people of Heilbronn argued about which faith to follow over a long time. In 1524 Johann Lachmann started to preach Luther’s ideas, but Mayor Konrad Erer, who kept the “old faith”, prevented Heilbronn from following the new teachings. However, this would change in 1528 with the election of his successor Hans Riesser.
In the year after his election, Heilbronn joined “The Protest at Speyer”, when fourteen imperial cities turned against a decision of the Imperial Diet. By expressing its concurrence with the Augsburg Confession on 14 July 1530, the city joined the circle of Protestant imperial cities for good.