By early July the Germans had amassed hundreds of thousands of men along with 3000 tanks. Opposite them, the Russians had nearly 2 million men ready to commit to battle and over 5000 tanks! The Red Air Force controlled the skies and could provide overwhelming fire power in support of the Soviet ground forces. In addition to this, the Soviets had constructed 7 layers of defense to contain and repel the German advance. The stage was set for a dramatic German defeat rather than the war winning success Hitler had in mind.
The Atlanta Cutlery blog