The logic of the German war effort: The Wages of Destruction, page 452:
However optimistic the Wehrmacht may have been in the assessment of its own capacities, the sheer size of the task facing them in the Soviet Union could not be denied. Most fundamentally, the Germans were grossly outnumbered. Even allowing for the unreliability of Stalinist statistics, the population of the Soviet Union cannot have been less than 170 million in 1941. The population of Germany was less than half that: 83.76 million people in 1939. Though the German army that invaded the Soviet Union probably outnumbered the Red Army troops stationed in the western sectors, the Germans had already conscripted virtually all their prime manpower. By contrast, the Red Army could call up millions of reservists. From the outset, therefore, it was clear that the Wehrmacht must not be sucked into a battle of attrition. And this imbalance of manpower was compounded by the enormous expanse of Soviet territory and the sheer impassability of the terrain. If the Red Army were able to withdraw in good order this would present Germany with insuperable problems. If on the other hand the coherence of the Soviet force could be broken, then the difficulty of maintaining communications would hamper their efforts to restore coherence no less than it impeded the German advance. Everything depended on deciding the battle, as in France, in the first weeks of the campaign. This was the assumption on which Barbarossa was premised. A massive central thrust towards Moscow, accompanied by flanking encirclements of the Soviet forces trapped in the north and south, would allow the Red Army to be broken on the Dnieper-Dvina river line within 500 kilometres of the Polish-German border. The Dnieper-Dvina river line was critical because beyond that point logistical constraints on the German army were binding. These limitations on Germany's new style of 'Blitzkrieg' had not been obvious in 1940, because the depth of operations required by Manstein's encircling blow (Sichelschnitt) had never exceeded a few hundred kilometres. The entire operation could therefore be supplied by trucks shuttling back and forth from the German border. On the basis of their experience in France, the Wehrmacht's logistical staff calculated that the efficient total range for trucks was 600 kilometres, giving an operational depth of 300. Beyond that point the trucks themselves used up so much of the fuel they were carrying that they became inefficient as a means of transport. Given the vast distances encountered in the Soviet Union, an operational depth of 300 kilometres was absurdly restrictive. To extend the range of the logistical system, the Wehrmachtt therefore split its motor pool into two segments. One set of trucks would move forward with the Panzer units and would ferry fuel and ammunition from intermediate dumps that would be resupplied by the main fleet operating from the borders of the General Government. By this expedient, it was hoped that the initial logistical range could be extended to 500 kilometres. By happy chance, this coincided exactly with the Dnieper-Dvina line. Haider, the army's chief of staff, was clearly aware of the fundamental importance of this constraint. In his diary at the end of January 1941 he noted that the success of Barbarossa depended on speed. 'Speed! No stops! Do not wait for railway! Do everything with motor vehicles.' There must be 'no hold ups', 'that aloneguarantees victory'. If serious fighting were to extend beyond this initial phase of the assault, it was clear from the outset that the Wehrmacht's problems would progressively multiply. If the Red Army escaped destruction onthe Dnieper-Dvina river line, the Wehrmacht would not be able to engage in hot pursuit, because it would first need to replenish its supply bases closer to the front line. After that, all operations would ultimately depend on the capacity of the Soviet railway system and the speed with which the Wehrmacht could build up forward supply bases to support Germany itself. Most German freight transport in the 1940s was accomplished by rail. For short distances, the horse was still essential in both town and countryside. Of course, the German motor vehicle industry might have been coaxed into producing more trucks. But the basic constraint on the use of motor vehicles in wartime Europe was not the supply of vehicles, but the chronic shortage of fuel and rubber. As we have seen, the fuel shortage by the end of 1941 was expected to be so severe that the Wehrmacht was seriously considering demotorization as a way of reducing its dependence on scarce oil. Everything therefore depended on the assumption that the Red Army would crack under the impact of the first decisive blow. It was hoped that, like the French, the Soviet forces would disintegrate, allowing them to be finished off in a series of encirclement battles. In the second phase of the operation, the German army would advance towards Moscow against disorganized opposition, precipitating the political collapse of Stalin's regime. In World War I it had taken almost four years for the combined forces of Austria and Imperial Germany to bring about the final disintegration of the Tsarist army. The assumption was clearly that the Communist regime was weaker and that the initial blow struck by the Wehrmacht would be far more dramatic. The racist assumptions built into this axiom of German planning are obvious. It was not, however, devoid of all rationality. Expressed most succinctly in terms of per capita GDP, there was a major developmental difference between Germany and the Soviet Union. According to the best modern estimates, German per capita GDP was two and a half times that in the Soviet Union in 1940. On this basis there was good reason to think that the huge quantitative advantage apparently enjoyed by the Red Army would turn out to be illusory. The far greater organizational capacity of theWehrmacht, the superior quality of its equipment and the greater training of its soldiers would carry the day. After all, this was the army tha thad defeated the combined forces of France, the British Expeditionary Force, Belgium and the Netherlands in six weeks. By launching its army against the Soviet Union, rather than prosecuting a direct air and sea assault on Britain and its backers in the United States, the Third Reich was not making an irrational strategic choice. It was deploying its best weapon against what still appeared to be the 'weakest link in the chain'.Not that the Germans were oblivious to the modernization of the Soviet Union since World War I. As the Wehrmacht's own economic staff well knew, Stalin's Five Year Plans had substantially transformed the geography of the Soviet economy. According to credible Western estimates we now believe that Stalin's regime increased total industrial output by 2.6 times between 1928 and 1940, and armaments outputgrew by vastly more. In their haste to industrialize, the Soviet planners had placed a large amount of investment in Western economic zones vulnerable to the German onslaught. But as the planners in Berlin fully understood, the First Five Year Plan of 1928-32 had established a new Soviet industrial base, safely to the east of the Urals, which had the capacity to sustain a self-sufficient population of at least 40 million people. Even if an invader managed to overrun a large part of the western Soviet Union, war production could continue at new industrial centres, such as the gigantic engineering works at Sverdlovsk. Overall,Soviet industrial capacity was clearly very substantial. In 1939 the German steel association put the Soviet Union well ahead of Great Britain, in third place behind the United States and Germany, with an annualoutput of 18 million tons of steel, compared to Germany's 23.3 million tons. And on paper at least the Red Army was a formidable force.Throughout the spring of 1941 Franz Haider recorded Hitler's ruminations about the Soviets' immense stocks of tanks and aircraft. Hitler knew that the Soviets had modern aircraft and 'mammoth' tanks with normous guns. But he comforted himself with the fact that most of the Red Army's equipment was obsolete. On the assumption that the Wehrmacht would be able to achieve a massed concentration at strategicpoints he was happy to predict that the Soviets would 'crumple under the massive impact of our tanks and planes'. No one, however, could deny the sheer vastness of the Soviet Union, and this alone made Barbarossa into a daunting proposition. Beneath the thick layer of hubris and optimism that surrounded the planning forBarbarossa, there were those in Berlin who expressed severe misgivings from the start. The doubts, interestingly, were of two kinds. There were at least some officers who questioned the feasibility of the operation itself. Significantly these included Field Marshal Fedor von Bock, commander of Army Group Centre, to whom fell the awesome task of crushing the main body of the Red Army en route to Moscow. By the end of January 1941, Bock was so concerned about the scale of the mission assigned to his army group that he forced Haider, the chief of army staff, to concede that there was a distinct possibility that the Red Army might escape beyond the Dnieper-Dvina line. What wouldhappen in this eventuality was the key question. One of the earliest wargames done to test the Barbarossa plan concluded that unless both the destruction of the Red Army and the capture of Moscow could be accomplished within a matter of months, Germany would face a 'long-drawn-out war, beyond the capacity of the German armed forces towage'.