He lost consciousness under the beatings but did not divulge any names; he was subsequently held at Fresnes Prison.[1] Debeaumarché was one of the so-called "77,000" (named for the prisoners' numbers, between 76,000 and 78,000), Fresnes prisoners who were transported by train from Pantin to Buchenwald on 15 August 1944.[5] He was moved to the underground factory of Mittelbau-Dora which produced V-1 flying bombs and V-2 rockets, and posing as an electrical engineer was put to work in the manufacture of the V-1. Maurice Naegelé, a Kapo in the tunnel assembly section, gained the trust of Debeaumarché by relating details of the resistance movement in France.