The Duchy of Brunswick, a German state since the tenth century, was a member state of the Germanic Confederation between 1815 and 1866. After the Prussian-Austrian War, Brunswick became a member state of the North German Confederation in 1867. Brunswick had allied with Prussia during the 1866 war against Austria and became a member state of the German Empire in 1871. The destiny of this Duchy is intertwined with the history of the Kingdom of Hanover.
Brunswick was comprised of three larger and six smaller portions of territory. A portion of the Harz Mountains was, until 1874, common to Brunswick and Prussia (Hanover) and known as the Communion Harz. In 1874, a partition was agreed to but the mines were still worked in common, four-sevenths of the revenues going to Prussia and the remaining three-sevenths to Brunswick.
The constitution was a limited monarchy. The throne was hereditary in the house of Brunswick Luneburg (Welf) but should that line go extinct, the throne would go to the House of Hanover (Guelph). The parliament of the duchy consisted of one house of 48 deputies, of whom communities elected 30, while the remainder represented the Evangelical church, the large landed proprietors, manufacturers and the professions.
The question of the succession to the Brunswick throne was acute after the 1866 war. Duke William of Brunswick was unmarried, and according to the existing conventions, upon the extinction of the elder line, the duchy would pass to the younger line headed by George, King of Hanover, who had just been deprived of his kingdom by the King of Prussia. In 1879, Duke William of Brunswick with the active support of Prussia concluded an arrangement for a temporary council of regency to take over the government on his own death. Moreover, according to the arrangement, should the rightful heir be unable to take possession of the duchy, the council was empowered to appoint a regent. Duke William died on the 18 October 1884, and the senior branch of the House of Welf became extinct. There had been strong Prussian pressure against having George V of Hanover or his son, Ernest, the Duke of Cumberland, succeed to a member state of the German Empire, without swearing loyalty to the Imperial German Constitution. Ernest, Duke of Cumberland, claimed Brunswick and promised to respect the Imperial German Constitution. This claim was disregard by the council of regency, and the Bundesrat declared that the accession of the Duke of Cumberland would be a threat to the peace and security of the empire. The council of regency chose Albert, Prince of Prussia, as regent. Albert died in September 1906, and after some perfunctory negotiations with the Duke of Cumberland, the Brunswick parliament chose Duke Johan Albert of Mecklenburg-Schwerin as regent in 1907.
Brunswick was the last state to enter into a military convention with Prussia. The Duke, who had allied with Prussia during the 1866 war, insisted on his personal control of the forces. Once the Duke died childless in 1884, the Prussian regent worked hard to finish the convention, which was signed on 18 March 1886. Prior to that time, units from Brunswick used the designation ducal, operating under the Protestant of the Constitution of the North German Confederation and they were subject to the Kaiser’s command only in time of war. The State also had the right to appoint officers separate from Prussia. Interestingly, Brunswick also maintained a different uniform prior to the convention wearing the black uniform of the Napoleonic tradition.
Agitation between the two royal houses of Prussia/Hannover continued and Prussia looked for a way to make a deal. The Duke of Cumberland's eldest son died of a car accident in 1912; the father renounced his claim to Brunswick in favor of his youngest son, who married the Kaiser's only daughter. The new Duke of Brunswick also named Ernst, swore allegiance to the Imperial German Empire, and was allowed to ascend the throne of the duchy in November 1913. Both he and his father were deprived of British titles derived from Hannover in 1919, for "bearing arms against Great Britain.”
Consuls were maintained for trade with Russia, Belgian, Great Britain, Italy, Austria-Hungary, Oldenburg, Russia, Saxony, Brazil, Mexico, Portugal, Paraguay, Rumania, Sweden, and Switzerland.
The capital was Braunschweig. The population in 1914 was 500,000. The religion was primarily Lutheran evangelical; but there was a large Roman Catholic community centered on the bishopric of North Germany. The Jews had several synagogues, with a rabbinate in Brunswick.
(Kaiserliches Statistisches Amt, 1914)