In the fierce Hildesheim Diocesan Feud of 1523, Lutter was again conquered by Duke Henry V of Brunswick and the Hildesheim prince-bishop John IV of Saxe-Lauenburg could only retain the locality of Ostlutter. During the Thirty Years' War, the Danish troops under King Christian IV retired to Lutter Castle, where they were defeated by Imperial and Catholic forces led by Count Tilly in the 1626 Battle of Lutter, a rout that changed the course of the Thirty Years' War.