The war was won after Tet, General Giap admitted that they had lost and no longer had the manpower or supplies to continue at any level needed to win and were going to push for a cease in hostilities UNTIL an American correspondent said the US had lost, that was Walter Cronkite. His statement created a uptick in demonstrations against the war and the north saw a glimmer of opportunity.
I bse this statement on Giap's book about the war.
