I once wrote a report as a military reservist concerning the logistical and supply issues on the Eastern Front. My inescapable conclusion after reading all of the sources mentioned in the various threads, the diaries of commanders in each of the three major attack fronts and recent commentary, was that the blitzkrieg, under any circumstances, couldn't succeed in Russia. Some of the German military leaders appreciated this fact. Admiral Rehder was extremely outspoken, and nearly lost his job early on. Hitler had already purged other perceived dissidents such as Fritsch and Blomberg, and kept more compliant Army leaders. Paulus, who would later command the 6th Army in defeat at Stalingrad, had authored a report that the Germans would exhaust supplies at Smolensk, and another Army report, startingly accurate, indicated there would be 250,000 German casualties at that point. (No one predicted that there would be 500,000 more by the end of 1941.) All of this was ignored by Hitler who baffled and thwarted his few remaining protagonists. Guderian himself had a better comprehension of Russian capabilities when he announced in the Fuhrer's presence that there were 10,000 enemy tanks on the border, but this too was discounted. Furthermore, it had already been startling to find that some French tank armour had already defeated German tank and antitank guns. Hitler knew this and had ordered the armour to be upgunned; however, this had not happened because of inefficiency and short timetables for which the Fuhrer himself can only be blamed. Ammunition shortages were occasioned by the number of hits (sometimes over 100 on a BT-7 tank) required for a kill, and tungsten HEAT or HEAP shells (which would allow a 37mm AT gun to easily defeat a T-34) were often in short supply. In the Center and South, the inability to easily defeat Russian armour was decisive.
I also analyzed the relative balance of forces. By totalling the German units that had to be shifted to other sectors to stave off Red Army counterattacks, it was possible to estimate that Moscow could have been taken by sustained effort, if 175,000 more troops and approximately 900 more tanks had been available. However, it likely would only have been enveloped, and the inevitable Russian counterattack would likely have broken into the city once again. The major benefit to the Germans would have been the capture of the major rail crossings which lay some 100 kilometers to the east, and this would have disrupted supply shipments from Murmansk and troop movements about the Moscow area. This would have prolonged the war,in my view, but would not have been decisive. The increased numbers of troops could have been obtained with sufficient time for training from Goehring's ill-fated Luftwaffe divisions, which wound up fighting useless battles after the turning point had already been reached. However, there was no way to increase the number of AFV's since Hitler (supposedly to avoid tipping off Stalin) refused to order the economy to war footing.
Additionally, Manstein's tanks, after taking the Dvina bridges, should have been directed eastword toward Veliki Luki, which would have removed the pressure from the north on Bock's sector. As it was, Manstein's Corps was hopelessly bogged in swampy terrain and forest, doing little during the crucial parts of the campaign. Leaving two battalions of tanks to act as Kampfgruppe would have sufficed in the North.
However interesting, these analyses do not resolve the German's dilemma, the lack of logistical and support systems for such a conflict. The other major conclusion I reached was that the German General Staff, in many ways ahead of its time and essential in the conduct of combined arms warfare, was an utter failure in planning Barbarossa. It had lacked the resolve to oppose the leadership changes ordered by Hitler, which were improper, scandalous and violated protocol. It failed in its duty to itself to prepare to conduct a military operation in a way that maximized the chances for success, and it failed in its feeble efforts to oppose Hitler's naive war schemes.