The Red Army and the Wehrmacht: How the Soviets Militarized Germany, 1922-33, and Paved the Way for Fascism by Iu. L. Diakov

Very technical and very detailed book about Werhmacht and Red Army cooperation. You'll read about the creation of tank testing grounds and schools for training tank crews, to artillery training grounds, checmical weapons testing, and even flight schools. Detailed reports from both sides about the advances being made, money being spent, research being conducted, etc. Worth the money if you have an interest in seeing exactly how much the Wehrmacht was able to accomplish in this period before Hitler came to power when the treaty between these two countries ended. Although I will say that the title is a bit misleading as the greatest part of the 'militarization' of Germany occured after Hitler came to power, not during the period described within the book.