THE STATUS OF NORTH VIETNAMESE INFILTRATION INTO SOUTH VIETNAM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78S02149R000200280004-5
• Release Decision: RIPPUB
• Original Classification: T
• Document Page Count: 14
• Document Creation Date: December 15, 2016
• Document Release Date: October 1, 2003
• Sequence Number: 4
• Content Type: REPORT

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THE STATUS OF NORTH VIETNAMESE INFILTRATION INTO SOUTH VIETNAM
Conclusions
1. During 1966, the infiltration of almost 78,000 men into
South Vietnam has been reported US military authorities, as of
25 January 1967, had confirmed the infiltration of about 39,500
of these and accepted as "probable" the infiltration of another
10,000. At least 21,000-2)+,000 of the personnel whose infiltration
has been confirmed came in as members of 12 North Vietnamese
infantry regiments whose arrival in South Vietnam during 1966 has
also been confirmed by MACV. Nine of these regiments came in via
the Laos corridor route and were assigned to portions of the
country from the southern I Corps area southward through III Corps.
The other three regiments and elements of a fourth regiment came
directly across the DMZ into the northern part of I Corps.
2. All 12 of these infantry regiments arrived in South
Vietnam in or prior to the summer of 1966. Since then, although
there have been a few reports of the arrival of additional
infantry regiments during the latter half of the year, none has
as yet been confirmed. Although it is possible that the arrival
of one or two additional infantry regiments since summer may
eventually be confirmed, the indices point to a sharp drop in the
infiltration of such units in the latter half of 1966. There have
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infiltration statistics.
infantry infiltration in contrast to the large number of such
indications which were evident during the heavy influx of these
units to South Vietnam in the first half of 1966.
3. In addition to the infiltration of infantry regiments
which took place during the first half of the year, there was a
steady influx of North Vietnamese support elements and other units,
some intended as replacements and fillers for Communist units
already in place in the South. During the latter half of 1966,
the infiltration statistics, as based on the evidence now available,
appear to suggest a drop off in such infiltration. However, we
think this is probably not the case. A large number of these
personnel are now carried under the "possible" category in current
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)-+. We believe that the most valid explanation for the drop in the
infiltration of regimental-size infantry units during the latter
half of 1966 is that Hanoi had achieved most of the basic force
structure planned for South Vietnam in 1966. It continued, however,
to send in support and filler personnel to flesh out this basic
force structure and provide replacements.
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5. It is therefore possible that Hanoi may see little value
now in infiltrating additional infantry regiments into South
Vietnam. We do not believe, however, that a cutback in infiltration
of major North Vietnamese units would necessarily be indicative
that North Vietnam is getting ready to negotiate or to discontinue
the war in the South. Available evidence continues to indicate
that North Vietnam is prepared to maintain over-all infiltration
at high levels and to prosecute a long war, if necessary, to
achieve its objectives. Nor do we believe that a change in tactics if there is one -- should be interpreted to mean that the Communists
intend to break up their large units or revert solely to guerrilla
warfare. We see no indications that Hanoi plans to break up any
of its existing regimental or divisional structures in the South,
even though these units have generally proved unable to carry out
large-scale mobile warfare. The mere presence of these Communist
main force units poses a substantial and continuing threat which
we believe that Hanoi will seek to maintain.
6. We thus believe that it is valid to conclude that Hanoi
still plans to continue vigorous efforts in support of the war
in South Vietnam and that, pending more definitive information
on the last quarter of 1966 and early 1967, it would be pre-
mature to assume that a further buildup in units and personnel
will not occur.
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I. Evidence Concerning Regimental Infiltration
1. Since December 1964, when the first regular North Vietnamese
Army Regiment arrived in South Vietnam via the Laos corridor, a
total of about 21 North Vietnamese infantry regiments moved into
Seventeen of these regiments moved
via the Laos corridor and three regiments and elements of a fourth
regiment entered South Vietnam directly across the DMZ. All of these
regiments arrived in South Vietnam in or prior to the summer of 1966.
Since then, there has been no confirmation of the arrival of
additional infantry regiments. The accepted total number of regiments
introduced during 1966 (12 infantry regiments) slightly exceeds the
number which arrived in 1965, and it is possible that more will be
accepted.
accepted in the MACV order of battle is the 52d Regiment;
2. The infiltration of the above units as well as the high
rate of total infiltration of North Vietnamese personnel as replace-
ments and in support units during 1966 (See Section II) have tended
to obscure what may be a significant, although possibly temporary
change in the pattern of infiltration of North Vietnamese units.
It appears that the infiltration of North Vietnamese regimental
size infantry units via the traditional infiltration route through
Laos dropped off sharply after the summer of 1966. The last
infantry regiment to arrive via the Laos corridor which has been
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Since then, however, there has been little evidence
arrival of more North Vietnamese infantry regiments except across
the DMZ. The movement of the three regiments
directly across the DMZ within a short period of time marked a
significant departure in the pattern of infiltration both in the
context of the route used and the size of force involved.
3. It is of course true that the confirmation of arrival of
units has in many cases been considerably delayed. The 32d
Regiment, for example, was not firmly identified until 10 months
after its arrival, and a delay of three to five months in firm
identification of a unit is about normal, particularly in cases
when the unit has not been engaged in a battle which has resulted
in the capture of prisoners and documents. The evidence obtained
only recently that the 165th Regiment was in South Vietnam for some
seven months before being firmly identified has again shown the
pitfalls of relying on currently available data to assess the
level of infiltration at any time.
ii. There are, however, other indices which support the
likelihood of a sharp drop in regimental infiltration through
Laos in the last half of 1966. During late 1965 and early 1966,
when the bulk of North Vietnamese regiments moved to South Vietnam,
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there were substantial indications from a variety of sources that a
large-scale augmentation of the North Vietnamese Army and infiltra-
tion of units into South Vietnam was under way, even though it
was not until some time later that the scale of the movement and
identification of the units could be established. These indications
included: some evidence from North Vietnam on expansion of the
armed forces and statements which implied that NVA units were to
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and documentary evidence of the
be committed to the South;
formation or planned formation of NVA divisions in the South. In
many (although not all) instances, there were indications of the
presence of NVA regiments in the South before they met the
criteria of order of battle acceptance.
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5. In contrast there were only a few indications during the
last six months of 1966 which would suggest continuation of any
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significant movement of NVA regiments through Taos. 'Mere is,
moreover, only limited evidence on the infiltration of regimental
forces in the DMZ area for the period September-December 1966.
During 4-6 October, some units were seen infiltrating the Western
DMZ/Laos border. While a regimental size force has not been
engaged, there have been repeated sightings and contacts with
platoon to battalion size units. This indicates that the area was
in use, although the size and type of force is unknown and no units
have been accepted in the OB.
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Captured documents, including some
excellent documentary information from Communist Military Region V
have provided no evidence that additional divisional structures
are present or in process of formation in that area and have
generally confirmed present OB holdings.
II. Infiltration of Personnel Other Than in Regimental Units
6. Except for the movements through the DMZ into Quang Tri
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(confirmed and probable) about 50,000,
Province, we believe that cumulative evidence strongly suggests that
the North Vietnamese have concentrated more on fleshing out their
basic force structure in South Vietnam (divisions and infantry
regiments) over the past six months than in adding additional
major infantry units. This does not mean, of course, that all
infiltration via the Laos corridor has ceased since the movement of
replacement groups and various types of support units has almost
certainly continued via this route. Several such units have been
accepted in OB, including at least one artillery regiment (the
84A Regiment) which arrived in about August. The function of units
of this type is to provide support to existing divisional and
regimental infantry units.
7. In terms of 1966 infiltration statistics MACV has accepted
Approximately
21,000-24,000 of the accepted infiltrators entered South Vietnam
in infantry regiments. The remainder entered as replacements or in
support/specialized units. If we consider only the infiltrators in
the "accepted" category, the average monthly infiltration rate during
1966 is about 5,2400.* When computed on a quarterly basis for the
first three quarters of the year the average monthly rate for each
quarter would be 8,000, 6,000 and 2,600. If both infiltration
categories -- accepted and possible -- are considered, the average
monthly infiltration rate is 7,900. Monthly averages for both
* Based on first nine months of 1966.
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categories when computed on a quarterly basis are 10,600, 7,500,
and 5,600, respectively.
8. Although a large number of the support units and other
personnel are still carried under the "possible" category in the
infiltration records the present evidence indicates that the entry
of many of them -- especially for the months from July through
October -- will eventually be confirmed. We believe, therefore,
that the confirmed rate of infiltration of other than regimental
units, at least through October, will eventually come into line with
the confirmed rate for this type of personnel for the first half of
the year. There are tentative indications, based on an incomplete
data, that the infiltration of support units and other personnel,
via both the DMZ and the Laos corridor route may have dropped off
during November and December. Reports have been received so far
on the possible arrival of less than 1,200 infiltrators. However,
reports as yet unconfirmed of a
possible step-up of infiltration in late December and in January
1967. We believe it is too early to conclude whether or not there
has been a significant change in the rate of infiltration since
October.
III. Possible Reasons For Change in Infiltration Pattern
9. The most valid explanation for the apparent change in the
infiltration pattern may be that the North Vietnamese, as of the
summer of 1966, had achieved most of the basic force structure they
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had planned for South Vietnam in 1966. By July 1966, Hanoi had a
force of seven divisions in being with at least 21 infantry
regiments. There was fairly good evidence that NVA and VC forces
had planned and hoped to implement a series of fairly large-scale
military operations during the latter half of 1966. Such an
action may have been planned, for example, in the northern
provinces of South Vietnam by a multi-divisional force coming
across the DMZ. Hanoi may have hoped such an offensive would
achieve a significant victory in this area or, at the least, divert
sufficient US forces to northern South Vietnam to permit Communist
units elsewhere in South Vietnam to launch major offensive
operations.
10. Pending the outcome of the operation, North Vietnam. may
have decided to cut back the infiltration of major units into areas
farther south. While the ultimate objective of the DMZ operation
is not entirely clear, the documents captured from the 324+B
Division and statements of its prisoners suggested, at least initially,
that the NVA did hope to "liberate" Quang Tri Province and perhaps
Thua Thien Province as well and establish a stronghold in the
northern area of South Vietnam which would facilitate further
infiltration and offensive operations. If so, the operation, like
other large-scale operations planned by North Vietnamese forces in
1966, largely failed to achieve its objectives (although it has
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tied down a considerable US force in the area) and resulted in at
least a temporary withdrawal of major elements of the invading
force into the DMZ or North Vietnam.
11. Elsewhere in South Vietnam, Communist attempts to launch
large scale actions were often thwarted when NVA/VC units were
simply unable to react rapidly or to change their tactical plans
in the face of US/FWMAF spoiling operations. In addition,
Communist units suffered from an inferiority in firepower, mobility
and logistics when opposed by US forces.
12. One additional possible explanation for the apparent decline
in regimental infiltration is that the Communists have decided to
give less emphasis to large-scale operations and more to small unit
actions and guerrilla-type warfare. There is some recent evidence
to support this, and the general lack of success which the
Communists had in launching large-scale operations over the past
year would suggest that they have somewhat belatedly made a more
realistic assessment of their capabilities and have recognized
that more emphasis on small-scale operations would be in their
interest. If in fact a decision has been reached to give primary
emphasis to small-scale operations, it might be that North Vietnam
would see little value in a further substantial buildup in the
number of regiments or divisions in South Vietnam. In this case,
infiltration over the next several months at least would probably
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be comprised largely of replacement groups, small, specialized
units, and the total number of infiltrators per month will probably
be oriented toward offsetting attrition rather than toward sub-
stantially increasing the number of major units as in late 1965
and early 1966.
IV. General Comment on Hanoi's Intentions
13. We do not believe that a cutback in infiltration of major
North Vietnamese units would necessarily be indicative that North
Vietnam is getting ready to negotiate or to discontinue the war
in the South. Available evidence continues to indicate that North
Vietnam is prepared to maintain over-all infiltration at high levels
and to prosecute a long war, if necessary, to achieve its objectives.
Nor do we believe that a change in tactics -- if there is one --
should be interpreted to mean that the Communists intend to break
up their large units or revert solely to guerrilla warfare. Although
the Vietnamese Communist press has carried a number of recent
articles implying greater attention to guerrilla-type operations,
these articles have also indicated that Communist tactics still
call for a combination of guerrilla and conventional warfare. An
article in the December issue of the Hanoi journal, Hoc Tap,
reiterated that the war in the South should be prosecuted by both
guerrilla and conventional methods on a long-term basis and
employing "flexible, varied strategies and tactics." One objective
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of intensive operations by guerrilla units, according to the Communist
press, is to facilitate the operations of main force units. Moreover,
it is possible to employ division and regimental-size units in
guerrilla-type operations without breaking up their organizational. integrity.
We see no indications that Hanoi plans to break up any of its existing
regimental or divisional structures in the South, even though these
units have generally proved unable to carry out large-scale mobile
warfare. The mere presence of these Communist main force units poses
a substantial and continuing threat which we believe that Hanoi will
seek to maintain.
14. We thus believe that it is valid to conclude that Hanoi still
plans to continue vigorous efforts in support of the war in South
Vietnam and that, pending more definitive information on the last
quarter of 1966 and early 1967, it would be premature to assume
that a further buildup in units and personnel will not occur.
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