In 1626, Christian IV, who was also Duke of Holstein, and thus a vassal of the Emperor, joined the anti-imperial coalition of the Republic of the Seven United Netherlands and the Kingdom of England under James I. After Christian IV was defeated at the Battle of Lutter am Barenberge, on 27 August 1626, by the troops of the Catholic League under Johan 't Serclaes, Count of Tilly, he and his remaining troops fled to the Prince-Archbishopric of Bremen and set up headquarters in Stade. Administrator John Frederick, Duke of Schleswig-Holstein-Gottorp, who was also Administrator of the Prince-Bishopric of Lübeck, fled to Lübeck and left the Prince-Archbishopric to be ruled by the Chapter and the Estates.