Barbarossa Derailed: The Battle for Smolensk 10 July-10 September 1941: Vol 2: The German Advance on the Flanks and the Third Soviet Counteroffensive, 25 August-10 September 1941, David M. Glantz.

Barbarossa Derailed: The Battle for Smolensk 10 July-10 September 1941: Vol 2: The German Advance on the Flanks and the Third Soviet Counteroffensive, 25 August-10 September 1941, David M. Glantz. 
Makes the case that the repeated Soviet counterattacks around Smolensk played a major part in shaping German strategy in 1941, proving that the Red Army would put up more resistance than expected, and diverting German attention away from Moscow and onto their flanks, where they would win a spectacular victory around Kiev. This volume focuses on the third Soviet counterattack and Guderian's move south towards Kiev. Heavily supported by documents, Glantz makes a very convincing case.
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