you are really misinformed about this,
Vietnam was always one country, until 1954 when it was split into north and south as a temporary agreement until national elections were to be held in 1956.
the viet minh were the anti-colonialist revolutionaries, were throughout the entire country for the entire first five decades of the 20th century until the defeat of the French colonialists at DienBenPhu in 1953, after which the Vietnamese issued a declaration of independence.
The Viet Cong came into existence in the late 1950's in the south in opposition to the breakaway South Vietnamese government.
The opposition to the South Vietnamese government was initially Viet Cong (NLF) then increasingly the North Vietnamese.
Your stubborn resistance to even the most basic facts is exhausting.