Upon the Hildesheim Diocesan Feud, Prince-bishop John of Saxe-Lauenburg had to cede Ringelheim to the neighbouring Principality of Brunswick-Wolfenbüttel in 1523. With the accession of Duke Julius it turned Protestant in 1568. During the Thirty Years' War, Imperial and Catholic troops tried to reconquer the former Hildesheim estates and defeated a Protestant army under King Christian IV of Denmark at the nearby Battle of Lutter in 1626. Duke Augustus the Younger of Brunswick-Wolfenbüttel finally restored Ringelheim to Hildesheim in 1641.