Foreign Relations of the United States, 1964–1968, Volume XXVII, Mainland Southeast Asia; Regional Affairs

220. Special National Intelligence Estimate¹

SNIE 57/1–67

Washington, December 14, 1967.

SIGNIFICANCE OF CAMBODIA TO THE VIETNAMESE COMMUNIST WAR EFFORT

The Problem

To estimate the extent and significance of Vietnamese Communist use of Cambodian territory in support of the Communist war effort in South Vietnam.

Conclusions

A. During the past year, increasing Allied pressure on the Communistsʼ military structure in South Vietnam has caused them to depend more heavily on the use of border areas. They use Cambodian territory as a sanctuary to evade Allied forces, as a refuge for rest, training, medical care, and in some degree as a route for the infiltration of personnel and military supplies from North Vietnam. We believe that Cambodian rice currently provides an important proportion of the food requirement of the VC/NVA regular forces in South Vietnam.

B. We still have no good evidence that military supplies or equipment are moved through Sihanoukville or other Cambodian ports to Communist forces in South Vietnam. But the Communists continue to smuggle small quantities of arms and other military equipment from Cambodia, some of which probably represents unauthorized diversions from arms imported by the Cambodian Government for its own forces.

C. If the Communists continue their present strategy, the importance of Cambodia to their war effort will probably grow in 1968, particularly as a sanctuary and as a source of rice. Denial of Cambodian sanctuary would probably not cause the Communist war effort to collapse in the neighboring areas of South Vietnam, but would make it much harder for the Communists to conduct effective military operations in these areas.

D. Over the past year, Sihanouk has become more aware of the extent of Vietnamese Communist use of Cambodia and more apprehensive over US intentions. He has made some small efforts to control activity in the border area but he lacks the military capability to impose effective measures. Sihanouk is likely to move toward more criticism of the US for real or imagined violations of Cambodian sovereignty, hoping to deter the US from carrying the war into Cambodian territory and thus avoiding direct involvement in the war.

Discussion²

1. Communist use of Cambodian territory for tactical sanctuary, for base areas, for infiltration of personnel, and as a source of supply does not appear to have changed fundamentally over the past year. However, as a consequence of growing pressure on the Communist military structure in South Vietnam, border areas have become of increasing importance in Communist strategy. Bases straddling the Cambodian-South Vietnamese border have facilitated Communist operations by providing safety for command and communication elements and refuge for Communist forces.

2. Base Areas.³ Of the major Communist base areas that make use of Cambodian territory, the most northerly is in the tri-border region where Laos, Cambodia, and South Vietnam meet. The Chu Pong and Se San bases in western Pleiku and southern Kontum provinces and the large War Zone C complex in northern Tay Ninh province also lap over into Cambodia. The Kas Kok base appears to lie principally in Cambodian territory, near where the Mekong River crosses into South Vietnam. There are less important base areas along the borders of the Cambodian province of Svay Rieng and the South Vietnamese province of Quang Duc and Kien Giang.

3. The functions of these base areas have remained about the same as last year. They include facilities for resupply and training prior to major engagements, and various medical facilities to treat wounded after combat. Some Communist combat regiments, which were subsequently engaged in the battles of Loc Ninh and Dak To, used Cambodian territory to refit and prepare for these attacks.

4. Tactical Sanctuary. The Communists continue to use Cambodian territory as a safe haven after combat, but the pattern varies and depends to a great extent on the circumstances of the engagements with Allied forces. During a major US search and destroy operation into War Zone C in early 1967, elements of COSVN took refuge in adjacent Cambodian territory. On the other hand, we have no evidence as yet that Communist combat elements withdrew into Cambodia after the Loc Ninh battle this fall.

5. Prior to the battle of Dak To, two elements of the Communist B–3 Front Headquarters and the NVA First Division moved north from the Chu Pong base to the tri-border area. At least part of this movement probably took place over trails on the Cambodian side of the border. During the actual battle the two elements of the B–3 Front Headquarters remained inside the northeastern tip of Cambodia, apparently directing the fight, and afterwards the First Division Headquarters and the headquarters of at least one of its component regiments moved into Cambodian territory for sanctuary.

6. Communist troops withdrawing into northeastern Cambodia penetrate less than 10 kilometers. Along the more populous southern half of the border, the penetrations of Cambodia are shallower, and smaller numbers of Communist troops are usually involved.

7. Infiltration of Personnel. In general, infiltration trails continuing southward from Laos follow the Cambodian-South Vietnamese border as far south as the Phuoc Long-Binh Long region of South Vietnam. They cross back and forth across the border in many places and lie less than seven kilometers inside the border on the Cambodian side. Along the trials are a number of way stations for rest, resupply, and medical attention. We have little evidence on the actual use of the trails for infiltration during 1967. We do know, however, that units in the B–3 Front and COSVN received replacements this year, and it is likely that many of these replacements used trails in Cambodia for some portion of their journey south.

8. Routes of Supply. We have observed few improvements on the numerous supply routes from Cambodia into South Vietnam in the past year. In general, movement on the roads appears to be about the same as last year while movement on the waterways in the northeast appears to have increased somewhat. The main direction of movement on these routes is north and east from Cambodia into Laos and the highlands of South Vietnam, and the supplies moved consist primarily of food. Some of the military supplies moving southward from Laos to Communist forces in South Vietnam are apparently portered through Cambodia over a system of trails. But there is still no good evidence that the Communists have been using Cambodian roads and waterways for this purpose.

9. Food. Food shipments from Cambodia to the Communist forces in South Vietnam and Laos have continued in 1967 but it is difficult to determine the quantities involved. We believe that the VC/NVA regular forces and administrative support troops in South Vietnam require about 180 tons of food per day, of which 15 to 20 percent probably comes from Cambodia either directly or via Laos. Cambodian food is also shipped northward into Laos to support the infiltration network there.

10. Cambodian rice is particularly important for Communist troops operating out of the tri-border, Se San, and Chu Pong base areas in the rice-deficit highlands. Communist troops in these areas are almost certainly unable to obtain sufficient rice locally or from the coastal plain. If Cambodian rice were not available, Communist forces in the tri-border base area probably could be supplied by shipments of North Vietnamese rice down the Laotian route system. This would substantially increase the daily tonnage of supplies moved and the movement would be more vulnerable to US aerial interdiction. It would, however, be exceedingly difficult to move sufficient rice farther south to the Se San and Chu Pong base areas, and Communist troops there might be forced to relocate. In the War Zone C complex, loss of Cambodian rice would probably force the Communists to allocate additional personnel to the task of collecting rice from nearby areas.

11. Weapons and Ammunition. Because of South Vietnamese controls, it is unlikely that any sizable amount of arms or ammunition is being smuggled up the Mekong to Phnom Penh and thence to South Vietnam. There is a greater chance that such material could be brought in through Sihanoukville or elsewhere along the coast. But despite occasional reports we still have no good evidence of such movements. We believe that in time we would have tangible indications of any continuing substantial shipments of arms and ammunition to Communist forces through Sihanoukville, should such movements occur. The Communists do, however, continue to smuggle small quantities of arms and other military equipment from Cambodia, some of which probably represents unauthorized diversions from Communist arms imported by the Cambodian Government for its own forces.

12. Chemicals and Other Supplies. Some potassium chlorate and other chemicals useful in the manufacture of explosives continue to reach the Communists via Cambodia. But we have little more information concerning the quantities involved than we did a year ago. The amount of drugs, communications equipment, and other supplies obtained from Cambodia appears to have increased slightly over the past year probably because increased Allied pressures make it harder to procure them within South Vietnam.

13. Outlook. If the Communists continue their present strategy, the importance of Cambodia to their war effort will probably grow in 1968, particularly as a sanctuary and as a source of rice. Denial of Cambodian sanctuary would probably not cause the Communist war effort to collapse in the neighboring areas of South Vietnam, but would make it much harder for the Communists to conduct effective military operations in these areas.

14. Sihanoukʼs Position. Over the past year, Sihanouk has become more aware of the extent of Vietnamese Communist use of Cambodia and he has made some small efforts to curtail it. Nevertheless, we do not believe he is likely to make a major effort, principally because the Cambodian Armed Forces are just not strong enough. The army totals only 32,000 and less than 9,000 regular troops are stationed in provinces along the entire 700 mile border with South Vietnam. In the two large northeastern provinces of Cambodia, moreover, there are only eight border posts and these are manned by small paramilitary units. Four of these are clustered around the junction of Route 19 and the South Vietnamese border, just north of the Communist Chu Pong base area. Along this sparsely manned frontier from Kontum to northern Tay Ninh are over 20,000 regular Communist troops.

15. Sihanoukʼs basic aim continues to be to avoid involvement in the war. He is increasingly apprehensive that the US will carry the war against the Communists into Cambodian territory. Since he cannot keep the Vietnamese Communists from using its territory, Sihanouk is likely to move toward more criticism of the US for real or imagined violations of Cambodian sovereignty, hoping thus to deter the US.

1. Source: Central Intelligence Agency, Job 79–R 01012A, ODDI Registry. Secret/[classification indicator not declassified]; Controlled Dissem. A note on the covering sheet indicates that the Central Intelligence Agency and the intelligence organizations of the Departments of Defense and State, and the NSA prepared this estimate. It was concurred in by all members of the USIB except representatives for the AEC and FBI who abstained on the grounds that the subject was outside their jurisdiction.
2. SNIE 57–67, “Significance of Cambodia to the Vietnamese War Effort,” dated 26 January 1967, Secret, provides a considerable amount of background and detail on Communist use of Cambodia, most of which is still valid. [Footnote in the source text. For SNIE 57–67, see Document 199.]
3. See centerspread map. [Footnote in the source text; the map is not printed.]