On the morning of 11 April 1945, American soldiers marched into Nordhausen. The SS had already long abandoned the Boelcke-Kaserne subcamp and the Dora main camp. Only a few hundred severely ill and dying inmates had remained behind. The Americans were deeply shocked by their dire condition.
In the Boelcke-Kaserne, the liberators found several hundred survivors amongst the 1,300 corpses. Many of them were beyond help. In the city of Nordhausen and the surrounding forests, the arrival of the U.S. troops saved the lives of numerous inmates who had fled the subcamp. German policemen and soldiers had continued trying to chase them down until the end.
The Americans reached the Dora camp the same evening. There as well, the sights they encountered were appalling. Of the 500 surviving inmates still in the camp, 200 died there over the weeks that followed. Others were taken to sanatoria where likewise not all of them could be saved.
Reference: Jens-Christian Wagner, Produktion des Todes: Das KZ Mittelbau-Dora, 3rd edition, Göttingen 2015.