The Tet Offensive also destroyed the National Liberation Front (popularly known as the Viet Cong) and handed the leadership of the war, by default, over to the North Vietnamese Communist leadership and its army. The NLF was not 100% a communist organization but was an organization and army that fought the US in South Vietnam and before the US they fought the French under a different name—the Viet Minh—and before the French, the Vietnamese fought the Chinese occupation that lasted for a thousand years before liberation from China. However, the communists organized the NLF as a blanket organization of many Vietnamese resistance groups to continue the fight against foreign occupation/intervention in Vietnam.
The Tet Offensive was fought primarily by the NLF and they lost about 75,000 troops compared to 6,000 U.S. and ARVN dead. History paints the Tet Offensive as a communist victory but that is wrong. The Tet Offensive saw half of the NLF’s troops killed. The victory was turning the American public against the war. It was a military loss and a PR victory. The Viet Cong lost that battle but the North won the war. After Tet, the North had to step up moving its troops and supplies into the South until the NVA made up 70% of the troops fighting there.
In 1968, the NLF or Viet Cong’s manifesto called for an independent, non-aligned South Vietnam and stated that “national reunification cannot be achieved overnight.” That all changed after Tet. In fact, that lost battle with the US handed the South over to the communist led North.