Framer has a point, the siege of Moscow would mean that now close to 2 million men would be held up trying to get control of 2 cities.

I would imagine that this would be catastrophic for the Germans as they would be trapped themselves in between the city's defenders and the relief force. The battle of Alesia rings a bell here, with a different ending.

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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