In March 1936, von Braun and Walter Riedel began consideration of much larger rockets than the A3 (under development at that time), which was merely a test vehicle and could not carry any payload.
[6] Along with Walter Dornberger, plans were drawn up for a more suitable and better equipped test site for large rockets at Peememünde, to take the place of the rather confined Kummersdorf.
[7] In mid-September 1943, Riedel and two others surveyed the Austrian Alps for a new site for rocket development to replace that at Peenemünde.
[8] The site consisted of a system of galleries driven into the mountains, and received the code name Zement (Cement).
From 29 May 1945 to 20 September 1945, following the end of World War II, Riedel was held in protective custody (Sicherheitshaft) at the US Third Army's internment camp at Deggendorf, situated between Regensburg and Passau.