MEMORANDUM FOR USIB PRINCIPALS FROM RICHARD HELMS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP82M00097R000800160001-6
• Release Decision: RIPPUB
• Original Classification: T
• Document Page Count: 16
• Document Creation Date: December 19, 2016
• Document Release Date: October 3, 2005
• Sequence Number: 1
• Publication Date: February 24, 1967
• Content Type: MEMO

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THE DIRECTOR OF CENTRAL INTELLIGENCE
WASHINGTON 25, D. C.
24 February 1967
The attached study entitled The Status of North
Vietnamese Infiltration into South Vietnam" was prepared
under the auspices of the United States Intelligence Board
at the request of the Secretary of State. It was originally
approved by the USIB on 9 February 1967 and updated with
your concurrence as of 24 February 1967.
It is forwarded herewith for your information and
appropriate dissemination.
Richard Helms
Director
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Regular "S"
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24 February 1967
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THE STATUS OF NORTH VIETNAMESE INFILTRATION INTO SOUTH VIETNAM
Conclusions
1. During 1966, the infiltration of almost 79, 000 men into South
Vietnam has been reported. * US military authorities, as of the latest
report had confirmed the infiltration of about 40, 000 of these and accepted
as "probable" the infiltration of another 10, 400. The remaining 28, 500
are listed in the "possible" category. At least 21, 000-24, 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
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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
collateral indications of regimental infantry
infiltration in contrast to the large number of such indications which
were evident during the heavy influx of these unites 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 replace-
ments 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
infiltration statistics. Available evidence indicates, however, that the
entry of many of them, at least through October, may eventually be
confirmed. There is insufficient evidence on the rate of infiltration of
support and other type personnel during the last two months of 1966 to
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conclude whether or not there has been a significant change in the rate
of such infiltration.
4. The US interdiction program undoubtedly has had an impact
on North Vietnam's infiltration and logistic support effort. The extent of
this impact is extremely difficult to assess. We believe that the most
valid explanation, however, for the drop in the infiltration of regimental-
size infantry units during the latter half of 1966 may be 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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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 South
Vietnam. (See Annex A.) 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.
2. The infiltration of the above units as well as the high rate of
total infiltration of North Vietnamese personnel as replacements 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
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corridor which has been accepted in the MACV order of battle is the 52d
Regiment; it departed North Vietnam in April and entered South Vietnam
in July 1966. Since then, however, there has been little evidence (from
prisoners, documents or other sources) which would indicate the arrival
of more North Vietnamese infantry regiments except across the DMZ.
The movement of the three regiments of the 324B Division 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 ex-
ample, 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.
4. There are, however, other indices which support the likelihood
of a sharp drop in regimental infiltration through Laos in the last half
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of 1966. During late 1965 and early 1966, when the bulk of North Viet-
namese regiments moved to South Vietnam, there were substantial
indications from a variety of sources that a large-scale augmentation of
the North Vietnamese Army and infiltration 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 ex-
pansion of the armed forces and statements which implied that NVA
units were to be committed to the South;
I reliminary reports from prisoners,
documents and other sources which indicated the arrival of NVA units
in South Vietnam; a large-scale expansion of the military
structure in South Vietnam; and documentary evidence of the 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. Similarly, the southward movement of the 324B Division
and of the "mid-65" division and indications that elements of the 341st
Division would also become involved in operations in the DMZ area
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were obtained on a reasonably current basis during the summer and early
fall of 1966.
5. In contrast there were only a few indications during the last six
months of 1966 which would suggest continuation of any significant move-
ment of NVA regiments through Laos. There 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. The last unit which can be identified
II
~s a likely candidate for infiltration is the "mid-65" division
which was deploying southward in August and which, if committed to
South Vietnam, will probably move through the DMZ.
FGaptured
documents, including some excellent documentary information from
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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.
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
(confirmed and probable) about 50, 500 and an additional 28, 500 are
carried in a "possible" category (see Annex B ). Approximately
21, 000-24, 000 of the accepted infiltrators entered South Vietnam in
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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, 500. * When computed on a quarterly basis for the first three
quarters of the year the average monthly rate for each quarter would be
9, 000, 5, 000 and 2, 600. If both infiltration categories--accepted and
possible-- are considered for this nine-month period, the average
monthly infiltration rate is 8, 000. Monthly averages for both categories
when computed on a quarterly basis are 11, 800, 6, 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.
Therefore, the confirmed rate of infiltration of other than regimental
units, at least through October, may 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
*Bas&d on first nine months of 1966.
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December. Reports have been received so far on the possible arrival of
less than 1, 700 infiltrators. However, there are
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.
9. The US interdiction program undoubtedly has had an impact on
North Vietnam's infiltration and logistic support effort. The extent of
this impact is extremely difficult to assess. The most valid explanation,
however, 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 had planned for South Vietnam in 1966.
1. 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 mult-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
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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 324B 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
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
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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 capa-
bilities 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 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 substantially
increasing the number of major units as in late 1965 and early 1966.
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ANNEX A
NORTH VIETNAMESE INFANTRY REGIMENTS IN SOUTH VIETNAM
Regiment
Infiltration Dates of Date Accepted Lo
Route Infiltration by MACV
cation & Subordination
in South Vietnam
95th
Dep NVN Oct 64+ 1 Oct 65 Ph
Arr SVN Dec 64+ 5t
u Yen Province
h Div (NVA)
Dep NVN Sep-
1 Nov 65 P
leiku Province
Oct 64 1s
t Div
18th
Arr SVN Jan 65
Dep NVN Dec 64+
Arr SVN Feb 65
Dep NVN Feb 65
Arr SVN Apr 65
3 Jul 65 T
9
1 Oct 65 B
3
ay Ninh Province
th Div (VC)
inh Dinh Province
d Div
Dep NVN Jul 65 17 Feb 66 B
Arr SVN Sep 65
3
inh Dinh/Quang Ngai
Provinces
d Div
33d
Dep NVN Jul 65 14 Nov 65 P
leiku Province
(101B)
Arr SVN Oct 65 1
st Div
66th
Dep NVN Jul- 21 Nov 65 P
leiku Province
Aug 65 1
st Div
6th
Arr SVN Oct 65
Activated in Quang Tri 10 Apr 66 Q
uang Tri Province
Province Oct 65 N
M
Dep NVN Aug 65 8 Mar 66 Q
Arr SVN Dec 65 2
orthern Sub-Region of
ilitary Region V
uang Tin Province
d Div
Dep NVN Dec 65 8 May 66 P
hu Yen Province
Arr SVN Feb 66 5
th Div (NVA)
Dep NVN Dec 65 1 Apr 66 K
ontum/Pleiku Provinces
Arr SVN Mar 66 1
0th Div
Dep NVN Jan 66 28 Nov 66 P
leiku Province
Arr SVN Mar 66 1
0th Div
14ist Dep NVN Jan 66 17 May 66 P
huoc Long Province
Air SVN Mar 66 7
th Div
ANNEX A
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Infiltration DaLccs 01'
Regiment Route Lui i LLintion
24th
Dep NN Jun 66
Arr SVN Mar 66
88th
165th
52d*
803d
31st
(2 ins)
Dep NVN Jan 66
Arr SVN Mar 66
Dep NVN Feb 66
Arr SVN Apr 66
Dep NVN Mar 66
Arr SVN Jun-
Jul 66
Dep NUN Apr 66
Arr SUN Jul 66
Dep NVN May 66
Arr SVN Jun 66
Dep NVN May 66
Arr SUN Jun 66
Dep NUN May 66
Arr SVN Jun 66
Dep NUN Aug 66
Arr SUN Aug 66
23 Jan 67
12 Jul 66
22 Jul 66
22 Jul 66
30 Nov 66
Location & Subordination
in South Vietnam
Kontum Province
Subord unknown
Kontum Province
10th Div
Quang Tin Province
2d Div
Phuoc Long Province
7th Div
Phuoc Long Province
7th Div
DMZ/Quang Tri Province
324+B Div
DMZ/Quang Tri Province
324B Div
DMZ/Quang Tri Province
324B Div
DMZ/Quang Tri Province
341st Div
-Arrived in Peiku in July and moved to Phuoc Long in September.
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Date Accepted
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31 May 66
15 Jun 66
23 Jul 66
23 Jan 67
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INFILTRATION TOTALS
(Reported as of 8 February 1967)
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MONTH
ACCEPTED TO
TAL POSSIBLE
TOTAL
~'-
Confirmed
Probable
(Accepted & Possible)
JAN
3, 482
1, 785 5,
267
2, 070
7, 337
FEB
6, 745
2,368 4,
113
2,410
11,523
MAR
11, 537
1,324 12,
861
3, 900
16, 7
61
APR
90
391
481
20
5
01
MAY
400
2, 890 3,
290
3,465
6, 7
55
JUN
10,460
600 11,
060
1, 315
12, 3
75
JUL
4, 238
120 4,
358
5, 506
9,8
64
AUG
1, 550
400 1,
950
3, 300
5,2
50
SEP
1,400
NA* 1,
400
300
1,7
00
OCT
115
500
615
4, 560
5, 1
75
NOV
NA*
NA*
NA*
630
6
30
DEC
NA*
NA*
NA*
1, 050
1, 0
50
TOTAL
40, 017
10, 378 50,
395
28,526
78,9
21
ACCEPTED
- ACCEPTED CONFIRMED:
A confirmed unit/group is
one which is determined to exist on the basis of information
provided by a minimum of two captives, returnees or
captured documents (any combination).
ACCEPTED PROBABLE: A probable infiltration unit/group
is one believed to exist on the basis of information which
can be evaluated as probably true provided by one captive,
returnee or captured document.
POSSIBLE - A possible infiltration group/unit is one which is believed
to exist on the basis of information which can be
evaluated as possibly true, even though no captive,
returnee or document is available to verify the report or
reports.
*NA - not available.
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