The German invasion of the Soviet Union ripped apart the fabric of Soviet society at its most vulnerable seam along the western and southwestern borderlands. In the case of the territories annexed in 1939–40 – the Baltic republics, Western Belorussia, Western Ukraine and Bessarabia – hostility toward the Soviet power, Russian carpetbaggers and Jewish and Polish minorities lay close to the surface. Bitter memories of forced deportations of indigenous political and cultural elites, anti-religious decrees and the beginnings of collectivization were recent and vivid. The national Communist parties in the borderlands, decimated by the purges four or five years earlier, were in no position to help sustain Soviet power or organize resistance to the invasion, or later to the Nazi occupation authorities.

For a decade Stalin had preached the doctrine of capitalist encirclement and the threat of war. He had eliminated any challenge to his personal dictatorship and secured full control over decision-making in foreign policy. He had tamed the Comintern; the danger no longer existed that foreign Communist parties might drag the Soviet Union into an international conflict by engaging in revolutionary adventurism. He had undertaken a rapid industrialization of the country, laying the foundations for a modern armaments industry. These were extraordinary achievements. Yet the means he had chosen to obtain his ends threatened to undermine the security of the state that he strove to guarantee. In the tension-filled years leading up the outbreak of the conflict, he had severely reduced the capabilities of the architects of the Soviet security system. The purges had cut deeply into the ranks of the weapons designers, the officer corps and the diplomats. Stalin remained obsessed with the security of the borderlands. But his suspicious nature was robbing him of the ability to assess the main source of danger or even to distinguish between imagined and real threats. This showed up most clearly in military planning and intelligence-gathering.