re: The forgotten lesson.
From Vietnam we could have learned that a person fighting on their homeland for their homeland with the support of the population against a foreign force can't be beaten. Subdued for a time, maybe, not beaten.
From WWII, and hundreds of other wars throughout history, we have learned that a person fighting on their homeland, with the support of their population, can have the living shit beaten out of them by a determined attacker who is not manacled hand and foot by a culture that believes that any act of war is a war crime. You might want to rework your theories on that.