 The vast majority of his subjects in Brandenburg, including his wife Anna of Prussia, remained deeply Lutheran, however.After the Elector and his Calvinist court officials drew up plans for mass conversion of the population to the new faith in February 1614, as provided for by the rule of "Cuius regio, eius religio" within the Holy Roman Empire, there were serious protests, with his wife backing the Lutherans.Resistance was so strong that in 1615, John Sigismund backed down and relinquished all attempts at forcible conversion.