White Sands, New Mexico
During World War II, Holderer worked for the German military as a low-level engineer under Wernher von Braun. When the war ended, the United States selected 100 of von Braun's men to help improve the United States' rocket technology as part of Operation "Paperclip". Shortly thereafter, another 20 were selected. Holderer was part of the second 20, arriving in 1945 as part of the second group. After a few years in White Sands, New Mexico, the Paperclip team moved to Redstone Arsenal, Alabama, in 1950.