By late August, it was evident that a German victory over Russia would not come quickly, if at all.
Hitler had ordered the invasion of the Soviet Union in June, against the advice of many of his military experts. His plan was to quickly take Russia in a rout, hitting the huge country with hard quick strikes to never give the Russians a chance.
But while the Germans had military superiority, they underestimated the ability of the Russian bear to bite back. The vast geography, the manpower advantage of the Russians, and the will of the Russian army and Russian people proved a formidable challenge.