 Although the Soviet High Command was alarmed by this , Stalin 's belief that the Third Reich was unlikely to attack only two years after signing the Molotov – Ribbentrop Pact resulted in a slow Soviet preparation . Since April 1941 , the Germans had begun setting up Operation <unk> to substantiate their claims that Britain was the real target . These simulated preparations in Norway and the English Channel coast included activities such as ship concentrations , reconnaissance flights and training exercises . 
