In the early stages of the Thirty Years War, the fighting troops were still made up of mercenaries until, in 1631, under the Calenberg duke, George, troops were organised for the entire Welf House of Brunswick-Lüneburg that, for the first time, provided a permanent standing army in the service of the dukes. After the disbandment of the common army for the overall House of Brunswick-Lüneburg in 1644, elements of its regiments joined the Principality of Lüneburg and formed the Lüneburg Army.