Rifleman interesting point and I must agree with the fact of how Stalin could not of foreseen that. However the rusian troops never melted or retreated they were all captured. Infact more then 3 million of them were captured or killed with the first 3 months. The troops that reinforced moscows front line came from siberia and heavy fortifications set up by the population.

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The war against Russia will be such that it cannot be conducted in a knightly fashion. This struggle is one of ideologies and racial differences and will have to be conducted with unprecedented, unmerciful and unrelenting harshness. -Adolf Hitler