Sino-Vietnamese conflicts (1979–1991)

The Sino-Vietnamese conflicts of 1979–1991 were a series of border and naval clashes between the People's Republic of China and the Socialist Republic of Vietnam following the Sino-Vietnamese War in 1979. These clashes lasted from the end of the Sino-Vietnamese War until the normalization of ties in 1991.

When the Chinese People's Liberation Army (PLA) 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". However, Chinese troops occupied an area of , which was disputed land controlled by Vietnam before hostilities broke out. In some places such as the area around Friendship Gate near the city of Lạng Sơn, Chinese troops occupied territories which had little military value but important symbolic value. Elsewhere, Chinese troops occupied the strategic positions of military importance as springboards to attack Vietnam.

The Chinese occupation of border territory angered Vietnam, and this ushered in a series of border conflicts between Vietnam and China to gain control of the area. These conflicts continued until 1988, peaking in the years 1984–1985.Joyaux, p. 242. By the early 1990s, along with the withdrawal of Vietnam from Cambodia and the dissolution of the Soviet Union, the relationship between the two countries gradually returned to normality. By 1991, the two countries officially proclaimed the normalization of their diplomatic relations, thereby ending the border conflicts.

Background

After 1979, there were at least six clashes on the Sino-Vietnamese border in June and October 1980, May 1981, April 1983, April 1984, June 1985, and from October 1986 to January 1987. According to Western observers, all were initiated or provoked by the Chinese to serve political objectives.Carlyle A. Thayer, "Security Issues in Southeast Asia: The Third Indochina War", Conference on Security and Arms Control in the North Pacific, Australian National University, Canberra, August 1987. The imminent threat of another invasion by the northern neighbor impelled Vietnam to build up an enormous defending force. During the 1980s, around 600,000–800,000 Vietnamese regulars and paramilitaries were estimated to have been deployed in the frontier areas, confronted by some 200,000Li, p. 259.–400,000 Chinese troops.

Throughout the conflict, the Vietnamese Vị Xuyên District had been the most violent front. According to cursory examination, seven divisions (the 313th, 314th, 325th, 328th, 354th, 356th, and 411th) and one separate regiment (the 266th/341st) of Vietnamese forces were involved on this battlefield in the mid-1980s. On the Chinese side, armies from seven military regions were rotated through this area to "touch the tiger's butt", a euphemism for obtaining combat experiences given by Chinese paramount leader, Deng Xiaoping. From 1984 to 1989, at least 14 Chinese armies had been substitutionally committed to the fight in the area (1st, 12th, 13th, 14th, 16th, 20th, 23rd, 26th, 27th, 38th, 41st, 42nd, 47th, and 67th).

Besides the use of regular forces, China also armed and trained ethnic resistance groups (especially from the Hmong people) to wage unconventional warfare against the governments of Vietnam and Laos. From 1985, Chinese support for these insurgents began to shrink, as the Laotian government initiated normalization of relations with China.

1980: Shelling of Cao Bằng

Since early 1980, Vietnam had orchestrated military operations during the dry season to sweep Khmer Rouge forces over the Cambodia-Thailand border. To put pressure on Vietnam to withdraw military forces from Cambodia, China had garrisoned several armies along the Sino–Vietnamese border. China also provided military training for some 5,000 anti-Laotian Hmong insurgents in Yunnan Province and used this force to sabotage the Muang Sing area in northwestern Laos near the Sino-Laotian border. Vietnam responded by increasing forces stationed at the Sino-Vietnamese border, and China no longer had the overwhelming numerical superiority as it did in its campaign in February 1979.

In June 1980, the People's Army of Vietnam (PAVN) crossed the Thai–Cambodian border during the pursuit of the defeated Khmer Rouge. Despite swift Vietnamese withdrawal from Thai territory, the Vietnamese incursion made China feel that it had to act to support its allies, Thailand and the Khmer Rouge. From 28 June to 6 July, in addition to outspoken criticism of Vietnam in diplomatic announcements, the Chinese continuously shelled the Vietnamese Cao Bằng Province.O'Dowd, p. 93. Small-scale skirmishes also took place along the border later in the year, with seven incidents occurring in the first half of October. China accused Vietnam of conducting cross-border raids against Chinese positions in the Luojiaping area, Maguan County, Yunnan Province on 30 September and 1 October, killing at least five Chinese. The Chinese then replied by an assault against Vietnamese positions in the same area on 15 October, in which they claimed to have killed 42 Vietnamese troops.

The Chinese shelling did not aim at any strategic military target or create any substantial damage in Vietnam. Vietnam felt that the conduct of military operations on a larger scale was beyond Chinese capabilities, and that this gave them a free hand to conduct military operations in Cambodia. The Chinese shelling was indicative of the type of conflict the Sino-Vietnamese border would see for the next 10 years.

1981: Battle of Hill 400 (Battle of Fakashan)

On 2 January 1981, the Vietnamese Ministry of Foreign Affairs proposed a ceasefire during the Lunar New Year festival. While this proposal was rejected by China on 20 January, the two sides continued the exchange of prisoners of war. The situation was relatively calm for the next few months.

In May 1981, ferocious fighting suddenly erupted in Cao Lộc District, Lạng Sơn Province, when the PLA launched a regiment-sized attack against a height known as Fakashan () to the Chinese and Hill 400 to the Vietnamese. In Hà Tuyên Province (now Hà Giang and Tuyên Quang Provinces), Chinese forces stormed the strategic peak designated as Hill 1688, or named Koulinshan () by the Chinese, and several other positions in its vicinity. Bloody engagements claimed hundreds of lives from each side. The two battles began on 5 and 7 May respectively; the one at Hill 400 persisted until 7 June with a succession of Vietnamese counter-attacks to reclaim the hill.Zhang, p. 147. To justify this military operation, China announced that the attacks were in response to acts of aggression by Vietnam during the first quarter of that year.

In retaliation, Vietnamese forces carried out raids against Guangxi Province on 5 and 6 May. A Vietnamese infantry company also struck the Mengdong co-operative commune in Malipo County, Yunnan Province. The Chinese claimed to have fought off these attacks and decimated hundreds of Vietnamese soldiers in Guangxi. On 22 May, they reportedly killed 85 Vietnamese soldiers in Koulin, Yunnan. In total, China claimed the deaths of about 300 Vietnamese soldiers during these border clashes. These numbers did not include losses in the battles at Fakashan and Koulinshan, in which Chinese reports accounted over 1,700 Vietnamese personnel killed or wounded.

Although the conflict raged on, China did not want to escalate and only deployed border guard units instead of regular troops into the battles. Western observers assessed that China was unlikely to teach Vietnam a "lesson" like in 1979, especially when Vietnam had strengthened its regular forces in border areas and had a clear advantage in terms of equipment. Other analysts pointed out that the upcoming rainy season and the recent cuts in its military budget would preclude China's carrying out a large-scale invasion.

1984: Battle of Vị Xuyên (Battle of Laoshan)

From 2 to 27 April 1984, in support of Cambodian rebel forces whose bases were being overrun by the Vietnamese Army during the K5 dry season offensive, China had conducted the heaviest artillery barrage since 1979 against the Vietnamese border region, with 60,000 shells pounding 16 districts in Lạng Sơn, Cao Bằng, Hà Tuyên, and Hoàng Liên Sơn Provinces. This was accompanied by a wave of infantry battalion-sized attacks on 6 April. The largest of them took place in Tràng Định District, Lạng Sơn Province, with several Chinese battalions assaulting Hills 820 and 636 near the routes taken during the 1979 invasion at the Friendship Gate. Despite mobilizing a large force, the Chinese were either beaten back or forced to abandon captured positions by the next day. Chinese documents later revealed that the ground attacks primarily served the diversionary objective, with their scales much lower than that reported by Western sources.

In Hà Tuyên, from April to July 1984, Chinese forces struck a strip of hills in Vị Xuyên District, named Laoshan () by the Chinese. Laoshan is a string of mountains running from the western part of Hill 1800 to another hill at an elevation of 1,200 m in the east. This easternmost hill has been referred to by the Chinese as either Dongshan () or Zheyinshan (), and was also the only position on the eastern bank of the Lô River where fighting occurred.O’Dowd, p. 100.

The PLA launched their assault at 05:00 on 28 April after intense artillery bombardment. The PLA 40th Division of the 14th Army crossed the border section to the west of the Lô River, while the 49th Division (probably from the 16th Army) took Hill 1200 on the eastern bank. The Vietnamese defenders, including the PAVN 313th Division and 168th Artillery Brigade, were forced to retreat from the hills. PLA troops captured the hamlet of Na La, as well as Hills 233, 685 and 468, creating a salient of thrusting into Vietnam. These positions were shielded by steep cliffs covered by dense forests along the Thanh Thủy River, and could only be accessed by crossing the exposed eastern side of the Lô River valley.

After 28 April, fighting remained continued in other places such as Hills 1509 (Laoshan), 772, 233, 1200 (Zheyinshan) and 1030, over which control constantly changed hands. The battle paused on 15 May, as Chinese forces had virtually secured these hills, but resumed on 12 June and again on 12 July as the PAVN mounted counter-attacks in an attempt to recapture the lost positions. Afterwards, fighting was gradually reduced to sporadic artillery duels and skirmishes. According to U.S. intelligence reports, Vietnamese forces failed to retake the eight hills. As the result, the PLA occupied 29 points within Vietnamese territory, including Hills 1509 and 772 west of the Lô River, as well as Hills 1250 and 1030 and Mount Si-La-Ca in the east. Along the border segment, the deepest Chinese intrusion was made at Hills 685 and 468 located approximately to the south. However, the Chinese failed to advance any further than southward, despite their outnumbering force. The heights continued to be contested in a string of later engagements, which lasted until 1986.

To defend the captured area, the PLA stationed two armies in the Vị Xuyên region, consisting of four infantry divisions, two artillery divisions, and several tank regiments. Chinese artillery positioned on the hills included field guns, howitzers, and 40-barrel multiple rocket launchers, while infantry regiments were equipped with guns and 100-D mortars. The PLA used tanks in some of the battles.

In June, the Vietnamese claimed to have annihilated one regiment and eight battalions of the PLA, equivalent to about 5,500 Chinese casualties. They raised the number to 7,500 by August. In contrast, the Chinese reported they had inflicted approximately 2,000 casualties on Vietnamese forces, while losing 939 soldiers and 64 laborers killed during the five-week offensive campaign in Laoshan.Li, p. 260. 1,080–3,000 Vietnamese deaths was additionally claimed by the Chinese after the action on 12 July. The Vietnamese admitted that the PAVN 356th Division alone suffered 600 killed on that day.