Foreign Relations of the United States, 1977–1980, Volume XXII, Southeast Asia and the Pacific

32. Paper Prepared in the Department of State¹

Washington, November 16, 1978

VIETNAM-KAMPUCHEA BORDER CONFLICT

Background

When Phnom Penh fell to the communists in 1975 the new Kampuchean leaders ordered Vietnamese troops based in northeastern Kampuchea out of the country. By June of that year the two nations were clashing over disputed border claims and offshore islands. Periodic clashes continued in 1976 and 1977.

In December 1977 major fighting developed in the Parrot’s Beak, a border area only 30 kilometers from Ho Chi Minh City. This was followed by a new surge of fighting on December 31 in the same area. Although the combatants pulled back from their furthest advances by mid-January, fierce fighting involving artillery, air strikes, and helicopter gun ships broke out again in June. It has continued since and armed clashes and casualties occur regularly on both sides of the border.

The outbreak of serious fighting between Hanoi and Phnom Penh in December 1977 helped to catalyze the falling out between Hanoi and Peking and brought about increased Chinese military assistance to Kampuchea and greater tensions along the PRC-SRV border. Sino-Vietnamese tensions have increased during October and November with almost daily charges by Hanoi of Chinese encroachment on Vietnamese territory. Hanoi’s most recent spate of accusations cannot be confirmed but they are symptomatic of escalating tensions between China and Vietnam as a result of the border conflict between Hanoi and Phnom Penh.

The international implications of the dispute took on added significance in early November with the conclusion of a Soviet-Vietnamese Treaty of Friendship and Cooperation, followed immediately by a hastily arranged visit of a high-level Chinese delegation to Phnom Penh. Vietnam, aware of the increased political complexity of the dispute, will carefully calculate its future moves. Nevertheless, the Vietnamese are likely to take strong military action in the current dry season.

Military Build Up

While we do not have full and precise information concerning the military situation in the Vietnam-Kampuchea border area, refugee reports and other sources, strongly suggesting the likelihood of increased fighting include:

—Armed clashes on both sides of the border have continued for well over a year with both sides taking heavy casualties. Reports of clashes dropped off somewhat in August and September, but picked up considerably in October and the first two weeks of November.

—In June and July 1978 the Vietnamese sharply escalated the level of fighting by conducting numerous air strikes some up to forty kilometers inside Kampuchean territory. During this period the Vietnamese apparently took and held the towns of Snoul and Mimot in eastern Cambodia. In recent weeks, the Vietnamese have moved aircraft from central Vietnam to bases closer to the major troop concentrations along the border.

—The prepositioning of supplies and equipment along with movement of additional troops to the border by both sides has continued throughout the summer and fall. We now estimate that Kampuchea has some 60,000 troops (14 understrength divisions) in place, while the Vietnamese have at least ten divisions totaling over 100,000 troops.

—Military recruitment of Vietnamese and Kampuchean youth has been stepped up including females 18–25 years of age. (Monthly draft calls are reportedly at their highest in years.)

—Reports from visitors to the border area indicate the Vietnamese and Kampucheans now regularly exchange artillery fire into each other’s territory. Kampuchean forces are reportedly employing 130 mm guns.

Current Military Situation

Battlefield activity has increased considerably during October and early November. Kampuchea has launched a number of attacks in the central highlands region of Vietnam in an apparent effort to keep Vietnamese forces off balance and forestall Vietnam’s offensive. Kampuchean units planted mines, destroyed roads, and shelled Vietnamese forces in border areas along route 19 during the month. They have also initiated attacks further south in the Duc Minh area penetrating some ten kilometers into Vietnamese territory.

In mid-October Kampuchean forces were instructed to try to take advantage of Vietnamese weaknesses on all fronts stemming from disorganization caused by heavy flooding. Interestingly, several sources indicate that the Vietnamese plan to use a Kampuchean attack as an excuse to launch “counterattacks” in retaliation. Presumably an offensive in the guise of a “counterattack” would be calculated by the Vietnamese to be less alarming to neighboring ASEAN countries.

The most intense fighting over the past month has been in the Parrot’s Beak portion of Kampuchea and adjoining portions of Vietnam’s Southwestern Tay Ninh province. Vietnam claimed in early October that forces from two Kampuchean divisions were defeated near Ben Cau. During the first part of October the Vietnamese attacks along route one inside Kampuchea were supported by airstrikes.

Fighting in the Mekong Delta area has been restricted by flooding for much of the summer and early fall but gradually increased during late October. Hanoi claimed to have killed or wounded 400 Kampucheans in clashes along and near the Mekong in mid-October. Late last month the Kampucheans apparently again began shelling Vietnamese border towns provoking the first Vietnamese airstrikes in the Delta in over two months.

In addition to military preparations, recent Vietnamese propaganda has increasingly referred to uprisings in Kampuchea led by insurgents opposed to the Pol Pot regime. We have no evidence to support such wide scale activity, but reports of isolated incidents involving insurgents have increased. Hanoi is known to be training Khmer insurgents who will presumably be reinserted into Kampuchea in connection with stepped up military efforts by Vietnamese forces in the border area.

Vietnam-China

Since mid-October Hanoi has repeatedly charged that Peking has sent troops to violate Vietnamese territory. Hanoi claims that major incidents occurred on October 13 and November 1. These accusations which include charges of “1000” Chinese troops entering Vietnamese territory are almost certainly exaggerated and were probably designed to set the stage for the November 3 Soviet-Vietnamese Friendship treaty and help Hanoi project the image of a smaller country forced to prepare for the contingency of a Chinese attack. Nevertheless, as the Vietnamese continue to prepare for an offensive in Kampuchea the risks of more serious incidents on the Sino-Vietnamese border increase. Peking has indicated on numerous occasions that it will send material support to Phnom Penh but does not intend to send troops to bail out the Pol Pot regime. For this reason China may feel compelled to initiate incidents along the Sino-Vietnamese border in order to warn Hanoi against precipitous action against Kampuchea. Despite some minor skirmishes by border guards, until recently neither Hanoi nor Peking had moved main force units to the border area. This week however, Hanoi reportedly has moved elements of a division formerly engaged in economic tasks in central Vietnam to positions close to the border. In addition Vietnam has reportedly fortified air defense positions near the China border further demonstrating its concern over Peking’s intentions.

1. Source: Department of State, Vietnam General Files for 1978, Lot 80D307, Box 6590, Briefing Papers (General) 1978. Secret. Drafted by Thomas P. Hamilton (INR/REA/SA).