THE COMMUNIST BUILD- UP IN NORTHERN SOUTH VIETNAM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP79T00826A001400010060-4
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 15
• Document Creation Date: December 15, 2016
• Document Release Date: March 8, 2004
• Sequence Number: 60
• Publication Date: November 22, 1966
• Content Type: IM

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22 November 1966
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INTELLIGENCE MEMORANDUM
THE COMMUNIST BUILD- UP IN NORTHERN SOUTH VIETNAM
DIRECTORATE OF INTELLIGENCE
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CENTRAL INTELLIGENCE AGENCY
Directorate of Intelligence
22 November 1966
The Communist Build-up in Northern South Vietnam
Summary
The build-up of North Vietnamese forces in and
around the Demilitarized Zone (DMZ) has clearly been
the most important strategic military move in Viet-
nam since the introduction of US combat troops. The
build-up has now been under way for about six months
and represents an attempt to extend North Vietnamese
control across the Demilitarized Zone into northern
Quang Tri Province.
The build-up has been pursued at considerable
cost to the Communists in the destruction of both
manpower and materiel. Currently, major elements
of the Communist forces in Quang Tri: are believed
to have retreated into and just north of the DMZ to
regroup for future operations.
NOTE: is memorandum was produced solely by CIA.
It was prepared by the Office of Current In-
telligence and coordinated with the Office
of Research and Reports, the Office of Na-
tional Estimates, and the Director's special
assistant for Vietnamese affairs.
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The creation of a stronghold in Quang Tri Prov-
ince would offer the Communists many military ad-
vantages. For example, North Vietnamese troops in
this area have considerably shorter supply lines
than units operating farther south. A handy sanctu-
ary from ground attack is also available in nearby
Laos and in North Vietnam. Moreover, the occupation
of northern Quang Tri Province by the Communists
would strengthen their military position in counter-
ing any US attempt to block infiltration or to mount
an invasion of the southern DRV.
One of major effects of the intensification of
Communist operations in northern South Vietnam and
the concomitant destruction of the neutrality of the
DMZ has been to establish a base from which to fight
a protracted war. This could be especially impor-
tant if developments elsewhere in the South continue
to go against the Communists. One of the aims of the
protracted war strategy is to tie down a significant
number of US and South Vietnamese units attempting
to meet the threat: posed by the build-up.
Despite the advantages to the Communists of op-
erations in Quang Tri Province, they also face some-
what the same dilemma there which they have recently
encountered elsewhere in South Vietnam in the opera-
tion of their main force elements. If they mount
large-scale operations, they are highly vulnerable
to allied air and ground firepower.. Thus, they are
almost forced to stay on the defensive, mounting
only small attacks or probing actions in the hope of
drawing allied ground forces into a position in
which the sudden ambush or the fierce, but short,
firefight can inflict high casualties on the allies.
If they do return to Quang Tri in force during the
next few months, the latter strategy is likely to
be the one they will follow.
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The Build-up
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regiments are believed to have infiltrated into west-
ern Quang Tri Province. Information on these addi-
tional units is quite limited, however, consisting of
at least two unidentified units equivalent in size to
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3. Since early October, there have been only
sporadic contacts with NVA elements in Quang Tri.
Communist activity, moreover, suggests that the major
Communist units are regrouping and requipping in prep-
aration for renewed. large-scale infiltration into
Quang Tri. The recent developments in Quang Tri are
reminiscent of Communist operations in the central
highlands adjacent to Cambodia. Communist units
there have repeated.ly moved back and forth across
the Cambodian border, fighting at times and places
of their own choosing, so as to cut the attrition
rate on their own forces.
e major enemy elements--several of them hard
hit by US ground and air attacks--have moved back
into or just north of the DMZ. Company-size enemy
elements, however, are still believed to be in the
Quang Tri salient. The pattern of past and present
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Military Advantages of the DMZ Build-up
6. Large-scale infiltration directly across the
DMZ offered a number of significant military advan-
tages to the Communists. In the first place, it
greatly facilitated the movement into South Vietnam
of a large enemy force in a short period of time. A
for example, stated that his unit's trip--
from the northern edge of the DMZ into Quang Tri's
mountainous interior--took only 12 days. In con-
trast, the trip through the Laotion corridor takes
about 40 days, often even longer than that. The
time factor may have been important in the decision
to move in, since Hanoi may have been hoping to take
advantage of the dislocation which followed the po-
litical unrest in April and May in the northern
provinces.
7. Use of the DMZ route was considerably safer
than the longer route through Laos. Communist troops
were less exposed to the effects of airstrikes and
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their commanders could exercise better command and
control during the relatively short march. More-
over, the troops were less likely to come down with
a debilitating sickness,
have indicated that high rates of sickness were a
major concern of the Communists after their troops
had been quartered in the Quang Tri jungle area for
a short time.
8. The movement of North Vietnamese troops into
Quang Tri Province also strengthened the Communist
military position for countering any US attempt to
block infiltration from North to South Vietnam.
Hanoi's concern over this possibility was first noted
in late 1965 and early 1966 in its propaganda replay
of press reports that the allies were planning an in-
filtration cordon from the South China Sea westward
into Laos roughly along the Route 9 axis. It is
probable that the build-up was designed,at least in
part, to impede any such US move. Documents captured
from units involved in the build-up declare an in-
tention to cut through the allied position along
Route 9.
9. It is also likely that the DMZ build-up is
intended to strengthen North Vietnam's defenses
against the threat of a US ground invasion of the
DRV. This threat has been repeatedly voiced in re-
cent months in North Vietnamese: propaganda,:. public
and private statements. It is thus probable that
Hanoi considers there is some necessity for con-
tingent planning against such an attack. Communist
supply dumps, bivouac areas, and other military fa-
cilities in this area have been constructed or ex-
panded. In addition, considerable priority is being
given to keeping the roads open and in building new
roads in the far southern DRV. Antiaircraft artillery
sites have appeared in increasing numbers and some
surface-to-air missile sites have also been intro-
duced close to the :DMZ.
10. The effect of the build-up on the North
Vietnamese side of the border--which has included
construction and expansion of military facilities--
has been to increase the capacity for supporting
Communist forces in the field in South Vietnam. By
building up and securing the highlands in Quang Tri
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and Thua Thien provinces, moreover, the Communists
have obtained fairly firm control over a corridor
which now extends from North Vietnam down into the
central mountain area of South Vietnam. Although
the movement of men and supplies along such a corri-
dor is still difficult, it will provide an alternate
infiltration route to the Laos panhandle.
indicate that one intention of the build-
up has been to establish new supply channels down
into central South Vietnam.
Other Aspects of the Build-up
11. The Communist position in Quang Tri offers
a formidable base area--in some of the worst fight-
ing terrain in the country--from which the Communists
can continue to protract the war, particularly since
developments elsewhere in South Vietnam continue to
go against them. With the sanctuary areas of Laos
and North Vietnam at their backs, Communist forces
are ideally suited to engage allied forces in the
area at times and places of their own choosing. One
of the basic concepts of the protracted war strategy
is to tie down as large a number of enemy troops as
possible. The Viet Cong had virtually achieved this
objective in mid-1965 when the South Vietnamese mili-
tary reserve was all but depleted. The large US
build-up since that time has exacerbated this prob-
lem for the Commiuni.sts; nevertheless, it continues
to be a major facet of their strategy.
12. By committing large forces into Quang Tri
Province, the Communists filled a vacuum in northern
South Vietnam and also provoked a major US and South
Vietnamese military response. Both major US Marine
headquarters were moved north from their bases at Da
Nang and Chu Lai to meet the growing Communist threat,
along with six marine battalions. In addition, a
battalion of the 173rd Airborne Brigade has been
moved to northern South Vietnam from the Saigon/Bien
Hoa area to provide a defense for one of the marine
base areas.
13. The marine preoccupation with northern
Quang Tri Province has pulled a sizable number of
troops away from pacification activities around their
enclaves at Chu Lai and Da Nang. This could open up
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opportunities for Communist guerrilla and local force
units in harassing and sabotaging friendly installa-
tions.
14. The strategy of a protracted war has re-
ceived increased attention in North Vietnamese propa-
ganda since mid-1965. The Communists began to stress
it at a time when their main forces in South Vietnam
were losing the military initiative and were being
placed on the defensive. The threat of a dry season
offensive by the Viet Cong,particularly in the central
highlands, was being effectively thwarted by US and
GVN spoiling operations. Enemy activity, for the most
part, was reduced to widespread terrorism, sabotage,
and harassment. The theme also reappeared at about
the time the 324th Division was beginning its prepara-
tions for infiltration.
15. It was about this time that a debate ap-
parently started among top-level North Vietnamese
leaders over basic military strategy in South Viet-
nam. The debate centered on the question of how
best to defeat the US in the military sphere. Pro-
tagonists included Senior General and politburo mem-
ber )1guyen Chi Thanh, who has been in South Vietnam
directing the war, and, possibly, North Vietnam's
long-time and popular Minister of Defense, General
Vo Nguyen Giap. These two men,, the only senior gen-
erals in the North Vietnamese Army, have been rivals
for years. It appears that some of the Hanoi leaders,
probably including Giap, questioned whether the in-
surgent forces were capable of maintaining their of-
fensive in the face of the rapid US build-up. They
suggested a shift to a basically defensive strategy--
one that would prolong the war--which would emphasize
the raiding and ambush tactics of the guerrilla.
Regular forces were to be shielded from-casualties
and maintained at all costs.
16. The substance of the military debate in-
volved, among other things, the question of the pace
and emphasis of the Communist military effort in the
South. Thanh argued forcefully in a July 1966 article
published in the party journal that the proper strategy
was to develop the ability to fight mobile warfare
similtaneously throughout the country. He pointed to
the period between mid-1964 and mid-1965 was the best
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example of how this strategy works. During that
period the Viet Cong were able, by launching nearly
simultaneous attacks both in the highlands and in
the flatlands around Saigon, to whipsaw the South
Vietnamese military reserve to the point where by
May 1965 the South Vietnamese forces were virtually
exhausted.
17. The defensive advocates, on the other. hand,
seem to have opted for the creation of a strong, multi-
divisional force, dug in and well supplied in a rather
well-dispersed region backing up on a larger and safer
rear area. Their tactic--based on their experience
against the French-is to entice allied forces into
the forward area of the base region, where entrenched
Communist forces are able to inflict severe casualties
upon the attacking forces. They will be willing,
moreover, to use large numbers of men and to take heavy
casualties as long as enough of the attacking force
could be destroyed, thus requiring the allies to with-
draw to their own base camp. Communist forces-.w.ould
then try to extend their base area or area of control
and begin the same process all over again. This
strategy also calls for intensive guerrilla warfare
behind allied lines in order to tie down as many troops
as possible. The enemy hopes by these tactics to stretch
allied forces thin, holding down the number which can be
committed to the assault on their major base areas.
18. It appears that the initial decision was made
prior to the 1965-66 dry season in favor of Thanh's
strategy of attempting to stay on the offensive with
persistent and large-scale attacks on US forces. Com-
munist forces, however, were unable to regain the initia-
tive during the last; dry season--a fact which probably
led to the renewal of the debate in the spring of 1966.
Given the recent developments near the DMZ, it appears
possible that proponents of the return to defensive
strategy are to be given a chance to prove their,
point in northern South Vietnam.
19. The probable objective of Communist forces
in the coming months in northern South Vietnam will
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be to exact maximum attrition of US and GVN forces
under conditions as favorable as possible to the
Communists. In addition, the Communists will prob-
ably conduct attacks on isolated or lightly de-
fended outposts such as the Khe Sanh Special Forces
camp, and then try to ambush friendly reaction
forces. Occasionally, larger battles may be fought
if friendly forces can be drawn into the prepared
Communist base areas between Route 9 and the DMZ.
Communist forces will, of course, attempt to take
advantage of any favorable tactical situation that
may arise.
20. Despite the advantages to the Communists of op-
erations in Quang Tri Province, they also face some-
what the same dilemma there which they have recently
encountered elsewhere in South Vietnam in the opera-
tion of their main. force elements. If they mount
large-scale operations, they are highly vulnerable
to allied air and ground firepower.. Thus, they are
almost forced to stay on the defensive, mounting
only small attacks or probing actions in the hope of
drawing allied ground forces into a position in
which the sudden ambush or the fierce, but short,
.firefight can inflict high casualties on the allies.
If they do return to Quang Tri in force during the
next few months, the latter strategy is likely to
be the one they will follow.
21. Alleged Communist plans to liberate Quang
Tri and Thua Thien provinces, as reflected in
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are more likely an exercise in propaganda rather
than a valid strategic aim of the Communists. Any
push in the near future by North Vietnamese forces
against populated coastal centers in Quang Tri
would almost certainly result in their defeat, in
the face of US firepower superiority.
22. Nevertheless, the sizable Communist forces
in this area still. retain the capability to launch
multiregimental and, perhaps, even multidivisional
attacks against friendly forces. They are not be-
lieved capable, however, of logistically supporting
a sustained offensive in the face of US air and
firepower superiority.
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