[4] However, Chinese troops occupied an area of 60 square kilometres (23 sq mi), which was disputed land controlled by Vietnam before hostilities broke out.

[5] 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.

[7] 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.

[9] 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.

[12] Since early 1980, China had orchestrated military operations during the dry season to sweep Khmer Rouge forces over the Cambodia-Thailand 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.

[13] 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.

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.

[8][19] 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.

[21] 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.

[22] 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.

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.

[8][23] Chinese documents later revealed that the ground attacks primarily served the diversionary objective, with their scales much lower than that reported by Western sources.

This easternmost hill has been referred to by the Chinese as either Dongshan (东山) or Zheyinshan (者阴山), and was also the only position on the eastern bank of the Lô River where fighting occurred.

PLA troops captured the hamlet of Na La, as well as Hills 233, 685 and 468, creating a salient of 2.5 kilometres (1.6 mi) thrusting into Vietnam.

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.

[31] 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.

In 1986, General Secretary of the Communist Party of the Soviet Union Mikhail Gorbachev called for the normalization of relations between Vietnam and China in a speech in Vladivostok.

[36][8] On 5 October 1987, a MiG-21 fighter jet of the Vietnam People's Air Force was shot down over the Chinese Longzhou County, Guangxi Province.

Despite heavy clashes in Vị Xuyên, the situation in other border provinces was relatively calm, and the Chinese did not deploy any of their regular units into the fight.

[38]: 258 During the five-year period from 1984 to 1989, the Chinese had fired over 2 million artillery rounds in Hà Giang Province, mainly in the area of 20 square kilometres (7.7 sq mi) of Thanh Thủy and Thạnh Đức Communes.