The Red Army 's focus on mobile operations in the early 1930s was gravely disrupted by Stalin 's purge of the military 's leadership . Since the new doctrines were associated with officers who had been declared enemies of the state , the support for them declined . Many large mechanised formations were disbanded , with the tanks distributed to support the infantry . After the German blitzkrieg proved its potency in Poland and France , the Red Army started a frantic effort to rebuild the large mechanised corps , but the task was only partly finished when the Wehrmacht attacked in 1941 . The huge tank forces , powerful only on paper , were mostly annihilated by the Germans in the first months of Operation Barbarossa . Another factor contributing to the initial defeat was that the Soviet post-World War I rearmament effort was started too early , and in 1941 the majority of Soviet equipment was obsolete and inferior to that of the Wehrmacht
purge of the military 's leadership
Great Purge
Military history of the Soviet Union