Gartered arms of Christian, Duke of Brunswick-Lüneburg and Bishop of Halberstadt
Christian was born in 1599 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.
A lover of cavalry warfare, Christian gained a reputation for cruelty and violence, especially against the Catholic church. His Catholic opponents dubbed him der Tolle ("the mad") due to his excesses in war. This has been disputed and considered by some to be undeserved as it was probably started by pro-Imperial pamphlets at the time. Christian died childless of wounds sustained in battle in 1626.