Cathedral chapter
Sigismund succeeded his elder brother, Frederick, in 1552 as prince-archbishop of Magdeburg and diocesan administrator of the Prince-Bishopric of Halberstadt. The administration of the Halberstadt see had been combined with the Magdeburg see since 1480. Because he was only 14 it was initially suggested that the Magdeburg Cathedral chapter could not elect him, so he was postulated. Until 1557, when he came of age, Count John George of Mansfeld was installed by the cathedral chapter to run the prince-archbishopric. On 21 January 1553 the young prince-archbishop, who had meanwhile been confirmed by Pope Julius III although he was Lutheran, was rendered homage by the nobility in Halle upon Saale. In the early years of the new schism the Holy See was not always aware who was seriously Lutheran, and still hoped the schism would abate again. Although Lutheran, Sigismund remained unmarried. In 1567 the remainder of the cathedral chapter converted to Lutheranism.