Viet Cong were destroyed utterly by 1969 or so. After the 1968 Tet (Vietnamese holiday) offensive, the VC ceased to exist as a meaningful fighting force. It was all NVA after that. South Vietnam fell in 1975 to a massive, mechanized, regular army invasion by PAVN, aided and abetted by demonicRATs in the US Congress, who refused to authorize any aid to South Vietnam.
So first a DEMOCRAT starts the war and forces a draft, and then fellow DEMOCRATS say “ah, hell with it, let’s go home?”