Sino-Vietnamese conflicts 1979–90

The Sino-Vietnamese conflicts of 1979–1990 were a series of border clashes between the People's Republic of China and the Socialist Republic of Vietnam following the Sino-Vietnamese War in 1979. These border clashes lasted from the end of the Sino-Vietnamese War in 1979 until 1990.

When Chinese troops withdrew from Vietnam in March 1979 after the war, China announced that they were not ambitious for "any square inch of the territory of Vietnam". In fact, Chinese troops occupied an area of 60 km2, which was disputed land controlled by Vietnam before hostilities broke out. In some places such as the area around Friendship Gate in Lạng Sơn Province, Chinese troops occupied territories which have no military value but important symbolic value. Elsewhere, Chinese troops occupied the strategic positions of military importance as a springboard to attack Vietnam. These areas, arguably, have always been considered as part of China despite of their actual control by Vietnam.

The Chinese occupation of border territory angered Vietnam, and this ushered in a series of fights between the two sides to gain control of the area. Border conflicts between Vietnam and China continued until 1988, peaking in the years 1984–1985. By the early 1990s, along with the withdrawal of Vietnam from Cambodia and the collapse of the Soviet Union, the relationship between the two countries gradually returned to normality.

Background
Since 1979, there were at least six big rounds of clashes on the Sino-Vietnamese border, in June 1980, May 1981, April 1983, April 1984, June 1985 and December 1986-January 1987. According to Western observers, all were initiated or provoked by the Chinese to serve their political objectives.

Shelling of Cao Bang
Since early 1980, Vietnam conducted military operations in the dry season to sweep small Khmer Rouge forces over the Cambodian-Thai border so that they would not be in Vietnamese-occupied Cambodia. To put pressure on Vietnam to withdraw military forces from Cambodia, China created pressure on the Sino-Vietnamese border by deploying troops there. China conducted military training for some 5,000 anti-Laotian H'mong troops in Yunnan Province and used these force to attack Muong Sing in northwest Laos near the Sino-Laotian border. Vietnam responded by increasing forces stationed at the Sino-Vietnamese border, and China no longer had the advantage of forces as they did on their campaign in February 1979. In June 1980, Vietnamese troops crossed the Thai-Cambodian border into Thai territory during the pursuit of defeated Khmer Rouge to Thai territory.

Despite rapid Vietnamese withdrawal from Thai territory, the Vietnamese incursion made China feel they must act to support their allied Thailand and the Khmer Rouge. On the days from June 28 to July 6, in addition to outspoken criticism of Vietnam in diplomatic announcements, the Chinese troops continuously shelled Cao Bằng Province in northern Vietnam. The Chinese shellings did not aim at any strategic military target at all, nor did these shellings create any substantial damage on Vietnam but was symbolic. Vietnam felt the conduct of military operations on a large scale was beyond the Chinese capabilities, so Vietnam could have a free hand to conduct military operations in Cambodia. However, Chinese shellings had shaped the types of conflict on the Sino-Vietnamese border in the next 10 years.

Johnson South Reef Skirmish
On March 14, 1988, a naval battle was fought between Vietnam People's Navy and People's Liberation Army Navy at the Spratly Islands. The battle resulted in the death of 64 Vietnamese soldiers and since then, China has controlled the Johnson South Reef of the Spratly Islands.