Sebastian Haffner, a famous German journalist, contemporary witness, and author of some elaborate books on the topic, states two theories what could have been a possible motive for Hitler:

* Hitler deemed the Western powers to expect German resistance concentrate on Russia, which would have meant easy orey for them. By violent resistance he wanted to force them to find an agreement with Germany, or to see Russia taking more territory than they had expected and agreed.

* Hitler's annihilation mania had already turned against his own people, the Germans. He could not forgive them to have lost his glorious war. While all good men were already KIA, only scum was left over. So he wanted to send as many as possible to death, and as many of the rest to be under bloody Soviet control.

Other theories:

* Hitler hated Stalin, but he somewhat learned to respect him for being the better of the two, while his hatred on Churchill and Roosevelt had grown. So he begrudged Stalin less and rather tried to kick the Westerners as much as he could.

* Who needs rational explanations??? Hitler was brainsick, his motivations were not comprehensible, it was just another madness.

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If someone tries to remove the speck in your right eye, will you turn to him the other also?