By the time our young, brave but green soldiers met the Viet Cong and North Vietnamese Army regulars in the steamy jungles of 60's Vietnam...
the Vietnamese had been schooled in the insidious ways of guerilla warfare with the invading Japanese pre WWII...then the colonial French post WWII until 1954...
with the Viet Minh victory under Ho Chi Minh. Before all that, China ruled medieval Vietnam for nine centuries and its exploitation had often triggered peasant uprisings.
You cannot beat a people like that into submission...the war of attrition they will bring to bear will sap your will and destroy generations of your youth.
.