Why do so many Americans think they won Vietnam?
It was lost by the South Vietnamese military, not U.S. forces! We trained equipped and financed their fight for independence! After we withdrew, their willingness failed the test at the Battle of Kontum (1975), when they abandoned the fight and fled from the advancing North Vietnamese Army. We defeated the communists in every major battle that occurred in that war!
Maybe because we decimated the communist forces to the point that they had to give up their ambitions for taking over the entire southeast Asian continent. We also slaughtered the Viet Cong during the 1968 Thet offensive and won big time any major battle we engaged in. 1st Tanks 1st Marines Da Nang April 1972.
