In the course of the Thirty Years' War troops of the Catholic League under Johan 't Serclaes, Count of Tilly conquered the Prince-Archbishopric in 1627/1628. The Leaguist takeover enabled Ferdinand II, Holy Roman Emperor, to implement the Edict of Restitution, decreed March 6, 1629, within the "Prince-Archbishopric of Bremen" and the "Prince-Bishopric of Verden". The convent of Zeven - still maintaining Roman Catholic rite - became the local stronghold for a reCatholicisation within the scope of Counter-Reformation. The nuns, who had converted to Lutheranism, were then expelled from the convent.