It existed for 92 days in the course of the dissolution of the Free State of Prussia after World War II until the foundation of Lower Saxony in 1946.

Nevertheless, on 1 November 1946 the British Military Government founded the new state of Lower Saxony from the unification of the German states of Brunswick, Oldenburg and Schaumburg-Lippe with Hanover, accepting the proposal of Hanoverian prime minister Kopf for a merger.

[1][2] He also discussed other territorial options for a Lower Saxony state which would have also included Bremen and the region of Ostwestfalen-Lippe.

Like the eastern parts of Hanover, the eastern areas of Brunswick which had fallen to the Soviet zone, including the former County of Blankenburg and the exclave of Calvörde (part of the Helmstedt district) were excluded and later integrated into the East German state of Saxony-Anhalt.

Only the Hanoverian Amt Neuhaus and those parts of Bleckede, which had also lain on Soviet-occupied territory, were again united with Lower Saxony after the German reunification in 1990.