We won it because our citizen soldiers, airmen, marines, and sailors were superb and willing to make sacrifice, and we had commanders who knew how to properly use them. They more than held their own against the professional armies of Germany and Japan. We also had an unmatched capacity to produce war material.
Sure we committed some atrocities and engaged in some barbarism. Given who and what we were fight that was inevitable. But that's not why we won, or who we were, which we proved again 3 years later with the Berlin airlift and Marshall Plan.
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