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

Plan “Barbarossa.”

In the year of our Lord 1189, Frederick I Barbarossa (Red Beard), Emperor of Germany and self-styled Holy Roman Emperor, took up the cross and led the Third Crusade against Saladin's Muslim armies that had just captured Jerusalem. Led by ironclad knights, the armies of Frederick's First Reich swept eastward through Hungary, the Balkans and Asia Minor, intent on liberating Christianity's holy places from infidel control. Over 700 years later, Adolf Hitler, Führer of his self-styled German Third Reich, embarked on a fresh crusade, this time against the Soviet Union, the heartland of hated Bolshevism. Inspired by historical precedent, he named his crusade Operation Barbarossa. In place of Frederick's ironclad knights, Hitler spearheaded his crusade with masses of menacing panzers conducting what the world already termed Blitzkrieg ('lightning war').
When Hitler began planning Operation Barbarossa in the summer of 1940, Germany had been at war for almost a full year. As had been the case throughout the late 1930s, Hitler's diplomatic and military audacity had exploited his foes' weaknesses and timidity, producing victories that belied the real strength of the Wehrmacht (Armed Forces) and Luftwaffe (Air Force). Before the Second World War began on 1 September 1939, Hitler's fledgling armies had reoccupied the Rhineland (1936), annexed Austria (1938), dismembered Czechoslovakia (1938) and annexed Memel (1939), all bloodlessly and with tacit Western approval. Once the war began, Hitler's armies conquered Poland (September 1939), seized Denmark and Norway (February 1940) and vanquished the West's finest armies to occupy the Netherlands, Belgium and France (May-June 1940), driving the British Army from the continent at Dunkirk in utter defeat. Protected by its formidable moat, the English Channel, and its vaunted High Fleet, Britain survived Hitler's vicious and sustained air attacks during the ensuing Battle of Britain, but only barely.
It was indeed ironic, yet entirely characteristic of Hitler, that military failure in the Battle of Britain would inspire him to embark on his crusade against Soviet Bolshevism. Even though defeat in the skies during the Battle of Britain frustrated his plans to invade the British Isles in Operation Sea Lion, Hitler reverted to his characteristic audacity. Inspired by his army's unprecedented string of military successes, he set out to achieve the ambitious goal he had articulated years before in his personal testament Mein Kampf, the acquisition of 'living space' (lebensraum) to which he believed the German people were historically and racially entitled. Conquest of the Soviet Union would yield that essential living space and, at the same time, would rid the world of the scourge of Bolshevism.
Militarily, however, the ground invasion and conquest of the Soviet Union was a formidable task. The German Wehrmacht had achieved its previous military victories in Western Europe, a theatre of operations that was well developed and distinctly limited in terms of size.It had done so by employing minimal forces against poorly prepared armies that were utterly unsuited to counter or endure Blitzkrieg and whose parent nations often lacked the will to fight and prevail. The conquest of the Soviet Union was an entirely different matter. Plan Barbarossa required the Wehrmacht to vanquish the largest military force in the world and ultimately advance to a depth of 1,750 kilometres (1,050 miles) along a front of over 1,800 kilometres (1,080 miles) in an underdeveloped theatre of military operations whose size approximated all of Western Europe. Hitler and his military planners assumed that Blitzkrieg would produce a quick victory and planned accordingly. To achieve this victory, the Germans planned to annihilate the bulk of the Soviet Union's peacetime Red Army before it could mobilize its reserves, by conducting a series of dramatic encirclements near the Soviet Union's new western frontier. Although German military planners began contingency planning for an invasion of the Soviet Union in the summer of 1940, Hitler did not issue his Directive 21 for Fall ['case' or 'operation'] Barbarossa until 18 December (see Appendix I). When he finally did so his clear intention was to destroy the Red Army rather than achieve any specific terrain or political objective:
The mass of the [Red] army stationed in Western Russia is to be destroyed in bold operations involving deep penetrations by armoured spearheads, and the withdrawal of elements capable of combat into the extensive Russian land spaces is to be prevented. By means of rapid pursuit a line is then to be reached from beyond which the Russian air force will no longer be capable of attacking the German home territories.1
Two weeks before, in one of many planning conferences for Barbarossa, Hitler had noted that, in comparison with the goal of destroying the Soviet armed forces, 'Moscow [is] of no great importance.'2 Both he and his military advisers were confident that, if his forces did destroy the Red Army, Stalin's communist regime in Russia would collapse, replicating the chaos of 1918. This assumption, however, woefully underestimated the Soviet dictator's control over the population and the Red Army's capacity for mobilizing strategic reserves to replace those forces the Germans destroyed in its initial vital encirclements. Only later in 1941, after the Red Army and Soviet government displayed resilience in the face of unmitigated catastrophes, did the Germans began believing that the capture of Moscow was the key to early victory.
To destroy the Red Army, Hitler massed 151 German divisions (including 19 panzer and 15 motorized infantry divisions) in the east, equipped with an estimated 3,350 tanks, 7,200 artillery pieces and 2,770 aircraft.3 The Finns supported Barbarossa with 14 divisions and the Rumanians contributed 4 divisions and 6 brigades to the effort, backed up by another 9 divisions and 2 brigades.4 The German Army High Command [Oberkommando des Heeres - OKH] controlled all Axis forces in the Eastern Theatre. The OKH, in turn, subdivided these forces into an Army of Norway operating in the far north and Army Groups North, Centre, and South with four panzer groups deployed from the Baltic Sea southward to the Black Sea. A German air fleet supported each of these four commands. Plan Barbarossa tasked Field Marshal Fedor von Bock's Army Group Centre, which included two of the four panzer groups (the Second and Third), with conducting the main offensive thrust. Advancing precipitously along the flanks of the Belostok salient, Bock's two panzer groups were to link up at Minsk to create the campaign's first major encirclement. Thus, the mass of German offensive power was located north of the Pripiat' Marshes, the almost-impassible ground that effectively divided the theatre into northern and southern regions. German military planners sought to exploit Russia's lack of decent roads and railroads laterally across the front and into the depths to prevent the mass of Soviet troops from regrouping from one sector to another or withdrawing eastward before they were surrounded. However, German intelligence overestimated the degree of Red Army forward concentration and was totally unaware of the groups of reserve armies that the Soviets were already deploying east of the Dnepr river. Once the border battles had ended, Plan Barbarossa required the three German army groups to advance along diverging axes, Army Group North towards Leningrad, Army Group Centre toward Moscow and Army Group South toward Kiev. Thus, from its inception, Plan Barbarossa anticipated dangerously dissipating the Wehrmacht's military strength in an attempt to seize all of Hitler's objectives simultaneously.
(Glantz 13-15)