Christian the Younger (September 20, 1599 – June 16, 1626), a member of the House of Welf, titular Duke of Brunswick-Lüneburg and administrator of the Prince-Bishopric of Halberstadt, was a German Protestant military leader during the early years of the Thirty Years' War. Fighting against the forces of the Imperial House of Habsburg, Habsburg Spain, and the Catholic League, he earned a reputation as a dangerous fanatic.
Christian was born at the Gröningen Priory near Halberstadt (in today's Saxony-Anhalt), the third son of Duke Henry Julius of Brunswick-Lüneburg (1564–1613) with his second wife Elizabeth (1573–1626), daughter of the late King Frederick II of Denmark. After his father's death, he was educated by his maternal uncle, King Christian IV of Denmark, and attended the University of Helmstedt. After the death of his brother Rudolf in 1616, Christian, at the age of 17, was elected his successor as Lutheran administrator of the Halberstadt bishopric. Though he did not obtain any confirmation by the Emperor or the Catholic Church, this position provided him the necessary finances to start a military career.
In 1620 Christian joined the army of Prince Maurice of Orange and fought in the Netherlands against a Spanish army. Later he raised his own army and, in liege to Frederick V, Elector Palatine, he carried out three significant battles: the Battle of Höchst (1622), the Battle of Fleurus (1622), and lastly at the Battle of Stadtlohn (1623). He participated in a number of plunderings and burnings along the France-Germany border and throughout the Netherlands. Christian fought alongside the Count of Mansfeld in the first two engagements, and suffered two losses to the Count of Tilly: an arguable one at Höchst, and his final one at Stadtlohn. Christian's major success was at Fleurus, where his actions directly led to the relieving of the Protestant stronghold of Bergen op Zoom.