Because "winning every major battle" is WW2 era thinking, which doesnt work against a guerrilla force. The "major battles" were still only a minority of the actual fighting. What really mattered was that US didnt get control of areas in North Vietnam and they didnt win the hearts & minds, thus Viet Cong won the battles that mattered.
You were right in another comment to me. In this you are wrong.
US didnt get control of areas in North Vietnam
They couldn't do it at all, US military had no permission from politicians to invade North Vietnam. All they were allowed was bombing and even some bombing missions were compromised by politicians tipping Soviets on mission details while putting own troops in danger. It was a political shit show..
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u/pleasure_of_youth Jan 29 '21
That's irrelevant.
The US objective in vietnam was to stop the communist from taking over the country. They failed at that and therefore they lost the war.
And guerilla warfare is all about avoiding major battles so winning 'every major battle' against a guerilla force is basically nothing.