By March 1945, Nazi Germany had long lost the war. The Nazi leadership nevertheless fought defeat by all available means. One of the obsessions that took hold in the final weeks of the war was the “Mittelbau Development Community”: an association of the Peenemünde rocket designers and the research departments of the major armaments manufacturers. They had all been assembled in the region around Nordhausen.
The centre of the development community was the town of Bleicherode. Wernher von Braun and his immediate staff also took up quarters there. On 6 March 1945, just five weeks before the Americans entered the region, von Braun applied for the joining of the Bleicherode and Kleinbodungen potash works to create gigantic underground research laboratories. It was clear who would build the underground facility: concentration camp inmates. Construction presumably never got underway.
Reference: Jens-Christian Wagner, Produktion des Todes: Das KZ Mittelbau-Dora, 3rd edition, Göttingen 2015.