The original plan for Barbarossa had called for a massive central thrust into Russia that would quickly capture Moscow and overwhelm the country. Army Group Centre was the most powerful of the three army groups and it made the quick progress towards Moscow that was expected. Army Groups North and South were also making rapid progress but not quite as quickly. It was now becoming apparent that by diverting some troops away from Army Group Centre they could could link up with the other groups and create vast encirclements around the Russian Army. But this meant deviating from the original plan and delaying the assault on Moscow. Major Gerhard Engel, Hitler’s Army Adjutant, was privy to Hitler’s thoughts at the time the critical decision was made:
28 July 1941
During a short stroll after the situation conference, F. [Fuhrer] spoke with Schm. and myself about further developments in the east. It was on account of these that he was not sleeping at night, since he was uncertain about many things. Within his breast two souls wrestled: the political-strategic, and the economic.
Politically he would say that the two principal suppurating boils had to be got rid of: Leningrad and Moscow. That would be the heaviest blow for the Russian people and the Communist Party. Goring had assured him that it could be done by the Luftwaffe alone, but since Dunkirk he [Hitler] had become a little sceptical. Economically speaking there were quite different objectives.
Whereas Moscow was a big industrial centre, the south was more important, where oil, wheat, more or less everything was located necessary to keep the country going. A land where milk and honey flowed.
One thing at least was absolutely required, and that was a proper concentration of forces. To use Panzers in fighting to demolish cities, that was a sin against the spirit. They had to operate in the open areas of the south. He had already started to hear the cries of those from whom they had been stripped; but that was neither here nor there.