Glantz, David M. Barbarossa: Hitler's Invasion of Russia 1941. Tempus Publishing Inc. Charleston. 2001.

Soviet War Planning: The Answering Strike.

Ironically, the Ribbentrop-Molotov Non-Aggression Pact, which Stalin and Hitler negotiated in August 1939, actually contributed to the catastrophic defeat the Red Army suffered during the initial stages of Operation Barbarossa. By signing the infamous agreement, Stalin hoped to forestall possible German aggression against the Soviet Union and, while doing so, create a buffer zone by seizing eastern Poland and the Baltic States. However, the Soviets' subsequent occupation of eastern Poland in September 1939 and the Baltic States a year later brought the Soviet Union into direct contact with Germany and forced the Red Army General Staff to alter its war plans fundamentally. Beginning in July 1940, the Red Army General Staff developed new war plans identifying Germany as the most dangerous threat and the region north of the Pripiat' River as the most likely German attack axis.5 Stalin, however, disagreed with these assumptions and in October 1940 insisted his General Staff prepare a new plan based on the assumption that, if it attacked, Germany would likely strike south of the Pripiat' River into the economically vital region of the Ukraine.6 With minor modifications, this plan became the basis for Mobilization Plan (MP) 41 and associated Red Army operational war plans.
Ordered by Stalin and prepared in early 1941 by G.K. Zhukov, the new Chief of the General Staff, State Defence Plan 1941 (DP 41) reflected the assumption 'that the Red Army would begin military operations in response to an aggressive attack.'7 Therefore, while defensive in a strategic sense, the plan and the military thought that it echoed was inherently offensive in nature. DP 41 and its associated mobilization plan required the Red Army to deploy 237 of its 303 divisions in the Baltic Special, Western Special and Kiev Special Military Districts and the 9th Separate Army, which, when war began, would form the Northwestern, Western, Southwestern and, ultimately, Southern Fronts.8 As a whole, Red Army forces in the western Soviet Union were to deploy in two strategic echelons. The first was to consist of 186 divisions assigned to four operating fronts, and the second was to include 51 divisions organized into five armies under High Command (Stavka) control. In turn, the four operating fronts were to deploy their forces in three successive belts, or operational echelons, arrayed along and behind the new frontier. The first operational echelon formed a light covering force along the border, and the second and third echelons, each of roughly equal size, were to add depth to the defence and conduct counterattacks and counterstrokes.
Mobilization difficulties in early 1941, however, precluded full implementation of DP 41. Consequently, on 22 June 1941 the first strategic echelon's three operational belts consisted of 57, 52 and 62 divisions, respectively, along with most of the Red Army's 20 mechanized corps deployed in European Russia.9 The five armies deployed in the second strategic echelon under Stavka control, which ultimately consisted of 57 divisions assembling along the Dnepr and Dvina rivers, was virtually invisible to German intelligence. Its mission was to orchestrate a counteroffensive in conjunction with the counterattacks conducted by the forward fronts. However, by 22 June 1941 neither the forward military districts nor the five reserve armies had completed deploying in accordance with the official mobilization and deployment plans.10 As in so many other respects, the German attack on 22 June caught the Soviets in transition. Worse still, Soviet war planners had fundamentally misjudged the situation, not only by concentrating their forces so far forward, but also by expecting the main enemy thrust to occur south of the Pripiat' Marshes. Thus the Red Army was off-balance and concentrated in the southwest when the main German mechanized force advanced further north.15
(Glantz 15-16)