Bremen-Verden, formally the Duchies of Bremen and Verden (; ), were two territories and immediate fiefs of the Holy Roman Empire, which emerged and gained imperial immediacy in 1180. By their original constitution they were prince-bishoprics of the Archdiocese of Bremen and Bishopric of Verden. In 1648, both prince-bishoprics were secularised, meaning that they were transformed into hereditary monarchies by constitution, and from then on both the Duchy of Bremen and the Duchy of Verden were always ruled in personal union, initially by the royal houses of Sweden, the House of Vasa and the House of Palatinate-Zweibrücken, and later by the House of Hanover. With the dissolution of the Holy Roman Empire in 1806, Bremen-Verden's status as fiefs of imperial immediacy became void; as they had been in personal union with the neighbouring Kingdom of Hanover, they were incorporated into that state. Territory and insignia The territory belonging to the Duchies of Bremen and Verden covered a rough triangle of land between the mouths of the rivers Elbe and Weser on the North Sea, in today's German federal states of Hamburg and Bremen (the Elbe-Weser Triangle). This area included most of the modern counties (German singular: Kreis) of Cuxhaven (southerly), Osterholz, Rotenburg upon Wümme, Stade and Verden, now in Lower Saxony; and the city of Bremerhaven, now an exclave of the State of Bremen. The city of Bremen and Cuxhaven (an exclave of Hamburg) did not belong to Bremen-Verden. The Land of Hadeln, then an exclave of Saxe-Lauenburg exclave around Otterndorf, was not part of Bremen-Verden until 1731. Stade was the capital. Bremen-Verden's coat of arms combined the arms of the Prince-Bishopric of Verden, a black cross on white ground, with those of the Prince-Archbishopric of Bremen, two keys crossed Bremen-Verden's seal), the symbol of Simon Petrus, the patron saint of Bremen. History At the beginning of the Thirty Years' War the predominantly Lutheran Prince-Archbishopric of Bremen maintained neutrality, as did most of the Protestant territories in the Lower Saxon Circle, a fiscal and military subsection of the Holy Roman Empire. The neighbouring Prince-Bishopric of Verden also tried to maintain neutrality, but, being part of the Lower Rhenish-Westphalian Circle, which was troubled by confrontation between Calvinist, Catholic and Lutheran rulers and their territories, Verden soon became involved in the war. In 1623 Verden's cathedral chapter, consisting mainly of Lutheran capitulars, elected Frederick II, Administrator of the Prince-Bishopric of Verden to