In Germany the campaign began in the west, where Archbishop of Cologne Hermann of Wied had converted to Protestantism in 1542. Emperor Charles began open warfare against the Protestant princes, estates, and cities allied in the Schmalkaldic League (see Philip of Hesse). Hermann was excommunicated on 16 April 1546, and was compelled by the Emperor to abdicate in February 1547. By the close of 1546, Charles V had subjugated South Germany. The victory at the Battle of Mühlberg, on 24 April 1547, established his imperial sovereignty everywhere in Germany, and the two leaders of the League were captured. The Emperor declared the Augsburg Interim as a magnanimous compromise with the defeated schismatics.