Viet Cong (VC) is derived from "Vietnamese Communist", and variously is considered either the military wing of the National Front for the Liberation of South Vietnam, or a generic and derogatory term for Communist forces in the Vietnam War after 1954. Depending on context, the term may make no differentiation between regular troops of the People's Army of Viet Nam (PAVN) of North Vietnam and guerrilla forces in South Vietnam. This is a complex issue, as many of the Communist guerrillas, after the 1954 partition of Vietnam, were members of the Viet Minh, which had been the military wing of the Communist-dominated nationalist forces when Vietnam was still a French colony, and then a "proto-state" member of the French Union.
Indeed, Douglas Pike, considered one of the authorities on the organization, entitled hs best-known book Viet Cong: Organization and Technique of the National Liberation Front of South Vietnam. The Vietnamese term dau trinh encompasses a combined political-military strategy, much as other revolutionary political organizations, such as Sinn Fein in Ireland, had overt or semi-overt political wings coupled with a covert military wing.
As the war entered its later stages, it moved from guerrilla to conventional warfare, PAVN forces formed the bulk of the Communist forces, for several reasons. First, there had been quite significant attrition of the Southern-born guerrillas and Viet Minh who had remained in the South after 1954. A large number of the Communist deaths during the 1968 Tet Offensive were considered Viet Cong rather than PAVN. Second, those experienced in guerrilla warfare were not necessarily trained to operate in the conventional military invasion.
Arguments that it is a derogatory term are fairly weak. As a practical matter, "member of the military wing of the National Front for the Liberation of South Vietnam" might take longer to say than it would for a sniper to shoot. U.S. forces in South Vietnam most commonly referred to the enemy as "Charlie", which is also the phonetic alphabet term for the letter "C". Several authors have commented that U.S. troops, after what was called "fire fight one", would sometimes start speaking of "Charles", in grudging respect for combat effectiveness.  If there was a common English derogatory term, it was "gook", which often did not differentiate between Vietnamese civilians, Communist fighters, and even the Army of the Republic of Viet Nam (ARVN).
Overall strategic command of Viet Cong operations could be traced to the North Vietnamese general staff, and a command group called the Central Office for South Viet Nam (COSVN).
- Douglas Pike (1970), Viet Cong: Organization and Technique of the National Liberation Front of South Vietnam, MIT Press
- Tourison, Sedgwick Jr. (1990). Conversations with Victor Charlie: an Interrogator's Story. Ballantine Books.