>Germany drove to Moscow as fast as they could and they failed to take Moscow because of Russian resistance.
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>Do not many experts assert that Hitler changed focus mid-campaign from taking Moscow to inflicting an economic defeat? What is your explanation for the drive towards Leningrad if you believe focus remained on reaching Moscow?

As it often happened armies attack on wide front, securing strategic flanks. More specifically, Hitler tried to seize both Moscow and Leningrad.