Foundation

The Diocese of Verden was founded around 800 in Verden upon Aller as a suffragan in the ecclesiastical province of Mainz. When the old Duchy of Saxony was carved up in 1180, some of the territory around the Sturnmigau' was erected as a state in Imperial immediacy. The Bishop of Verden, in addition to his spiritual duties, was, ex officio, the temporal ruler of the Prince-Bishopric of Verden. The first Prince-Bishop — Tammo of Verden — ruled an area that was about a quarter of the extent of the diocesan territory. In 1195 Prince-Bishop Rudolph I founded the castle of Rotenburg upon Wümme as a stronghold against the neighbouring Prince-Archbishopric of Bremen. Later the castle took on the function of a prince-episcopal Residenz.

The bishops, and hence the prince-bishops, were elected by the cathedral chapter. However, the papacy tried to influence the elections and sometimes succeeded in getting their candidates elected. Such candidates, who were usually not local men, did not enjoy local support and were seen as Landfremde or alien.

From the early 16th century the prince-bishopric belonged to the Lower Rhenish–Westphalian Circle (colloquially: Westphalian Circle), a fiscal and military subsection of the empire. Verden sent its representatives to the Imperial Diet and to the Imperial Circle. While Verden, like the neighbouring County of Hoya, was a member of the Westphalian Circle, other adjacent territories, such as the Duchy of Brunswick-Lüneburg and the Prince-Archbishopric of Bremen, were part of the Lower Saxon Circle. At times, the prince-bishops also ruled the Prince-Archbishopric of Bremen in personal union. In order to maintain their two seats in the diets, the states of Bremen and Verden were never formally united in a real union. The same is true for the collectively governed Duchies of Bremen and Verden which emerged in 1648 from the two secularised prince-bishoprics.

The Reformation

From 1558, a gradual change of confession to Lutheranism took place across the Verden diocesan. Within the hochstift, the Reformation was concluded with the enactment of a church ordinance by Administrator Eberhard von Holle, in 1568. In 1630, during the Thirty Years' War, a Catholic bishop, Francis of Wartenberg, took over again as a consequence of the Edict of Restitution, but was only able to hold office until 1634. Thereafter, the Catholic Church was only represented there by the Apostolic Vicariate of Northern Missions.

Disestablishment

In 1648, by the terms of the Peace of Westphalia, the state was disestablished. In its place, a principality of the Empire was established that was ruled by the Swedish crown. The Principality of Verden was in turn disestablished in 1712. During this period, the principality was ruled in personal union with the territory of the former Prince-Archbishopric of Bremen; they were informally known as the Duchies of Bremen-Verden or more formally the "Duchy of Bremen and Principality of Verden".