they were forcing them to work until allies started gaining ground. germans realized they would eventually be liberated and decided to kill them before that happened. also germans are simply barbaric people - they kill for the fun of it and just because they can. hitler gave an order to destroy paris just out of spite, it served no practical purpose. the order was never carried out, but still. they did in warsaw right before leaving it just cause they could. don't try to rationalize it, a german does evil just because he enjoys the feeling of impunity.
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