After Eric's death in 1584 Calenberg-Göttingen was again ruled by the Wolfenbüttel line of the Welfs. In the Thirty Years' War the brother of Duke Frederick Ulrich, "mad" Christian, brought the war to the state. After Danish troops under King Christian IV, who was then commander of the Lower Saxon Circle, was defeated by the general of the Catholic League, Tilly in the Battle of Lutter, Tilly occupied the whole principality in 1626. Only the cities of Brunswick and Hanover could not be captured.