H-Net Reviews: Since the Wehrmacht had been unable to assemble the necessary forces by the time Blue was to start, the Army High Command (OKH) designed a complicated, staggered operation in which each phase had a specific goal, thus setting the stage for the achievement of the next step in the plan. The initial phase aimed at seizing the city of Voronezh, just east of the Don, which would allow flank protection to the forces advancing to the east (it also, in the event, sparked furious Soviet counterattacks, since German forces could easily turn north toward Moscow, as anticipated by Stalin). In the next stage, German forces would move south along the Don to trap and annihilate the bulk of Soviet forces in the region….
The events of July, and how they were interpreted, resulted in two key decisions late that month. Hitler, having concluded that the Red Army had at last been destroyed, issued the key directive of the campaign on July 23, the one which guaranteed that the Germans could not achieve their goals. Impatient at the slow pace of the step-by-step operation, and fully aware of the time pressures on Germany (that summer he constantly worried about an early second front in France), Hitler decided to speed things up by splitting the German attack: while Army Group B would continue to advance on Stalingrad, Army Group A would seize Rostov and leap into the Caucasus. Rather than the careful, step-by-step campaign in which each phase ensured the success of the next, the Führer had now sent two army groups off on their own, in diverging directions and with inadequate forces to realize their goals. The Germans had barely been able to supply one advance at a time; with the same catastrophic logistical system, they were now to supply two, with the second moving hundreds of miles into the trackless steppe of southern Russia. With their shoestring operation, all had depended on everything going according to plan; Hitler now changed the plan.