I wouldn't disagree with you that US authors classify the Viet Cong as an "insurgency". That view is not new (soup was eaten off a knife long before Nagl) - because it fit the US political posture. That was that SVN was an independent nation state with legitimate governace over all of the population in SVN. Thus, any citizen of SVN who took up arms against the RVN was an "insurgent".
E.g., a brief Wilfian definition of insurgency (here):
There were at least two problems with the US-GVN approach. One (more minor) is that it gave credence to the NLF (National Liberation Front) as as a South Vietnamese group, independent of the DRV government and the Lao Dong (CP of Vietnam). We know that was nonsense, but it led to bi-furcated thinking - an "insurgency" threat in the South and a conventional threat from the North.They become an insurgency when they try to replace the existing government as that which exercises authority over them, and use violent means to secure that policy.
The second was the VietComs did not look at the war in that manner. In their view, the "existing government" in the South (RVN) was not "that which exercised authority over them". "Them" being the Viet Cong. Their government was the government of Hanoi, ruling over a unified Vietnam (albeit half-occupied by the US and its SV puppets). In essence, their argument was the same as that of the French Resistence - their government was the Free French in exile; the Vichy government being a puppet of the Germans.
What followed from these two very different positions was even more critical. The VietCom effort (a combined PAVN and NLF effort, which was FM 31-21 in effect) had Unity of Command - Hanoi's control over the NLF was exercised through COSVN. Our (US and RVN) efforts (counterinsurgency vs NLF; conventional vs PAVN/NVA; and bombing of NV) had no unity - in effect, three separate wars (further divided by your annual iterations - another of our defaults).
Fortunately for us, the other events in SE Asia of the 60s and 70s turned out well for us (US) - so, we clearly won in SE Asia as a whole region. But, SVN was lost (I don't concede that was due to US failures alone - see this post) to what I perceive as being a superior concept of that armed conflict by the VietComs on a strategic level.
Dwell on my iconoclastic suggestions for a bit. E.g., that we should have treated the NLF and Viet Cong as an unconventional force (it using concepts similar to FM 31-21), as opposed to treating it as an "insurgency".
Best regards
Mike
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