The deterioration of Sino-Vietnamese relations was gradual, commencing perhaps most dramatically with Richard M. Nixon's 1972 visit to China (which Hanoi later called the beginning of China's betrayal of Vietnam), but in the mid-1970s the signs of an impending breakdown were barely discernible. Until 1977 the Vietnam-Cambodia dispute appeared to the outside world to be purely bilateral and China's strategic considerations seemed only distantly connected to the skirmishes taking place on the Vietnamese-Cambodian border. The Chinese in the 1976-77 period were preoccupied with internal affairs, including the deaths of Mao Zedong and Zhou Enlai, the arrest of Mao's widow, and the return to power of Deng Xiaoping. As the situation between Vietnam and Cambodia deteriorated, the signs of a potential SinoVietnamese rift became clearer the more Cambodia's strategic importance for both China and Vietnam. appeared at risk. Aside from risking the return of the Khmer Rouge, Vietnam, viewed a disengagement from Cambodia as paramount to inviting China to create a two-front threat by establishing a foothold on a second Vietnamese frontier. In China's view, Vietnam's sustained presence in Cambodia not only precluded such an accomplishment, but conferred territory, once administered by an acknowledged Chinese ally, to the authority of an historic Asian adversary that was closely allied with a contemporary superpower rival, the Soviet Union.

Vietnam's and China's shared modern experiences, namely their common exploitation by colonial powers and adaptations to communist ideology, did little to alter Vietnam's historical view of China, which was colored by lengthy periods of Chinese conquest and domination. During the Second Indochina War, China acted as North Vietnam's closest ally, but, according to later Vietnamese statements, the Chinese tried to dominate the relationship from the beginning. Vietnam's desperate need for Chinese assistance forced it to maintain good relations with Beijing for the duration of the war, despite Vietnamese suspicions that China's ultimate purpose was to weaken Vietnam (see The Chinese Millennium Nine Centuries of Independence , ch. 1).

After the end of the Second Indochina War, underlying tensions between the two countries surfaced, and in 1978 a number of issues converged to bring the relationship to the breaking point. In addition to the growing dispute in Cambodia, these issues included territorial disagreements and Vietnam's treatment of its own largest minority group, the Hoa (see Glossary) or ethnic Chinese, who numbered nearly 2 million.

The territorial dispute involved primarily delineation of territorial waters in the Gulf of Tonkin and sovereignty over two archipelagos in the South China Sea, the Paracel and the Spratly Islands (the Xisha and the Nansha in Chinese the Hoang Sa and Truong Sa in Vietnamese). A border dispute on land (over fewer than sixty square kilometers) was responsible 1000 e for the relatively steady occurrence of low-level bÍÍÍÍÍÍÍÍorder clashes involving crossborder violations and the exchange of small-arms fire. In 1958 the two governments decided to defer settling their border differences until after victory had been achieved in the South.

Disagreement over territorial waters in the Gulf of Tonkin stemmed from agreements reached between China and France in 1887, stipulating a territorial limit of no more three nautical miles. These agreements had been adequate until 1973, when Hanoi announced to Beijing its intention to negotiate contracts with foreign firms for the exploration of oil in the Gulf of Tonkin. The disputed islands in the South China Sea assumed importance only after it was disclosed that they were near the potential sites of substantial offshore oil deposits. In January 1974, Chinese military units seized islands in the Paracels occupied by South Vietnamese armed forces, and Beijing claimed sovereignty over the Spratlys. Following their conquest of South Vietnam in the spring of 1975, units of the People's Army of Vietnam (PAVN) nevertheless moved to occupy the Spratly Islands previously held by the Saigon regime.

Vietnam's treatment of the Hoa became an issue in 1978, when Hanoi instituted a crackdown on the Chinese community because of its pervasive role in domestic commerce in the South and its alleged subversive activities in the North. The government action forced an unprecedented exodus of thousands of Hoa across the border into China, prompting Beijing to accuse Vietnam of persecuting its Chinese community and of breaking a 1955 agreement that called for the gradual and voluntary integration of the Hoa into Vietnamese society. The situation was aggravated when Vietnam denied landing privileges to three Chinese ships dispatched to evacuate Hoa seeking voluntary repatriation to China. Beijing threatened Hanoi with unspecified retaliation, and Chinese activities on the Sino-Vietnamese border escalated.

The deterioration in bilateral relations became evident when China reduced in May 1978 and then cancelled on July 3 its remaining aid projects in Vietnam. The officical announcement followed by only a few days Hanoi's admission on June 29 to the Soviet-dominated Council for Mutual Economic Assistance ( Comecon--see Glossary). A few months later, in November 1978, a new era in Soviet-Vietnamese relations began with the signing of a Treaty of Friendship and Cooperation that called for mutual assistance and consultation in the event of a security threat to either country. The document facilitated Soviet use of Vietnamese airports and port facilities, particularly the former United States military complex at Cam Ranh Bay (see The Armed Forces , ch. 5). In return, it assured Vietnam of economic and military aid for the anticipated invasion of Cambodia and established the Soviet Union as a deterrent to possible Chinese intervention in Cambodia.

Vietnam's decision to align with the Soviets together with its invasion of Cámbodia and mistreatment of the Hoa, provoked Beijing to "teach Hanoi a lesson." A "self-defense counterattack," mounted by China along the Sino-Vietnamese border on February 17, 1979, ended less than a month later, on March 5, when Chinese leaders announced that their objectives had been met and proceeded to withdraw their forces (see History , ch. 5). Despite the Chinese boast of having shattered the myth of Vietnam's invincibility, the invasion effected little more than the diversion of some Vietnamese troops from Cambodia. The bulk of the resistance reportedly was offered by local Vietnamese border units and regional forces. Outnumbered, they performed well, exposing significant weaknesses in Chinese tactics, strategy, logistics, equipment, and communications. In the final analysis, the results were far from conclusive. Peace negotiations were initiated following th 8f2 e disengagement of forces, but broke down several times before being discontinued in December 1979.

The Cambodian crisis, too, remained stalemated, and Vietnamese dependence upon the Soviet Union continued. In 1987 tensions along the Sino-Vietnamese border erupted in sporadic fighting. China believed that the Cambodian conflict would serve Chinese interests by draining the Vietnamese economically and weakening Hanoi. China's sustained pressure on Vietnam's northern border would also tax Vietnam militarily, while satisfying ASEAN's requests for Chinese assistance in the conflict and providing Chinese armed forces with invaluable combat experience. Consequently, Vietnam's dry-season campaigns to eliminate CGDK resistance base camps along the Thai-Cambodian border were generally matched by corresponding Chinese acts along the SinoVietnamese border. China issued vague threats to Vietnam of a "second lesson" in the mid-1980s but as of 1987 had not acted on these threats.

China imposed the removal of Vietnamese troops from Cambodia as a precondition to improved Sino-Soviet relations, and diplomatic activity in late 1986 indicated that Vietnam might mend its differences with China in the event the Soviets moved closer to the Chinese. Despite Hanoi's desire to ease tensions with Beijing, however, it was not willing to do so at the expense of its position in Cambodia.

Data as of December 1987