If you would like to read more about the background (from the Western intelligence perspective) of the German experience in Russia's early missile program, I would suggest you attempt to track down (maybe a university library, or from the British Interplanetary Society itself) the following two-part article serial. If memory serves, part 1 had a bunch of illustrations with it. It was all part of Operation Dragon Return.
P. Pesavento, Before Sputnik: A Glimpse into What Western Intelligence Knew About Soviet Rocketry and Personalities. Part 1. Space Chronicle 63 (JBIS Supplement 2):63-91, 2010.
P. Pesavento, Before Sputnik: A Glimpse into What Western Intelligence Knew About Soviet Rocketry and Personalities. Part 2. Space Chronicle 64 (JBIS Supplement 1):25-44, 2011.