SS General Hans Kammler, who as an engineer had constructed several concentration camps, including Auschwitz, had a reputation for brutality and had originated the idea of using concentration camp prisoners as slave laborers in the rocket program. Arthur Rudolph, chief engineer of the V-2 rocket factory at Peenemünde, endorsed this idea in April 1943 when a labor shortage developed. More people died building the V-2 rockets than were killed by it as a weapon. Von Braun admitted visiting the plant at Mittelwerk on many occasions, and called conditions at the plant "repulsive," but claimed never to have witnessed any deaths or beatings, although it had become clear to him by 1944 that deaths had occurred. He denied ever having visited the Mittelbau-Dora concentration camp itself, where 20,000 died from illness, beatings, hangings and intolerable working conditions.
In Wernher von Braun: Crusader for Space, numerous statements by von Braun show he was aware of the conditions but felt completely unable to change them. A friend quotes von Braun speaking of a visit to Mittelwerk:
It is hellish. My spontaneous reaction was to talk to one of the SS guards, only to be told with unmistakable harshness that I should mind my own business, or find myself in the same striped fatigues!... I realized that any attempt of reasoning on humane grounds would be utterly futile.
When asked if von Braun could have protested against the brutal treatment of the slave laborers, von Braun team member Konrad Dannenberg told The Huntsville Times, "If he had done it, in my opinion, he would have been shot on the spot."
Others claim von Braun engaged in brutal treatment or approved of it. Guy Morand, a French resistance fighter who was a prisoner in Dora, testified in 1995 that after an apparent sabotage attempt that von Braun ordered a prisoner to be flogged, while Robert Cazabonne, another French prisoner claimed von Braun stood by as prisoners were hanged by chains suspended by cranes. However, these accounts may have been a case of mistaken identity.
Proof exists however that von Braun himself went to KZ Buchenwald to pick slave laborers (letter to Albin Sawatzki dated August 15, 1944). Former inmate Adam Cabala reported: "[...] also the German scientists led by Prof. Wernher von Braun were aware of everything daily. As they went along the corridors, they saw the exhaustion of the inmates, their arduous work and their pain. Not one single time did Prof. Wernher von Braun protest against this cruelty and bestiality during his frequent stays at Dora. Even the aspect of corpses did not touch him: On a small area near the ambulance shed, inmates tortured to death by slave labor and the terror of the overseers were piling up daily. [...] But Prof. Wernher von Braun passed them so close that he was almost touching the corpses"