Sino-Vietnamese War

Sino-Vietnamese War--- Third Indochina War
The Sino–Vietnamese War, also known as the Third Indochina War, was a brief but bloody border war fought from February 17 to March 16, 1979 between the People's Republic of China (PRC) and the Socialist Republic of Vietnam.
The PRC launched the offensive in response to Vietnam's invasion and occupation of Cambodia, which ended the reign of the PRC-backed Khmer Rouge, and Vietnamese raids in Chinese territory near the border. Both sides claimed victory in the last of the Indochina Wars of the twentieth century.
Reason for starting the Sino-Vietnamese War

The expulsion and persecution of Ethnic Chinese in Vietnam from late 1970s was one of the reasons, though not a primary one cited by China for starting the Sino-Vietnamese War. The reason cited for the invasion was the supposed mistreatment of Vietnam's ethnic Chinese minority and the Vietnamese occupation of the Spratly Islands (claimed by the PRC). The Third Indochina War followed the unsolved problems of the earlier wars. PRC, which was under Deng Xiaoping, was growing increasingly defiant.
Aftermath of the War
In the short run, China lost thousands of troops and millions of yuan were lost in overhead, delaying completion of their 1979-80 economic plan. They caused extensive damage to the Vietnamese countryside and infrastructure. The war did not alter Vietnamese policy in Cambodia; the Khmer Rouge regime in Cambodia was still ousted and replaced by a puppet government. The Chinese were forcibly reminded of their troops' lack of training and tactical coordination.
Border skirmishes continued throughout the 1980s. In 1999 after many years of negotiations, China and Vietnam signed a border pact, though the line of demarcation remained secret. There was a very slight adjustment of the land border, resulting in land being given back to China. Vietnam's official news service reported the implementation of the new border around August 2001.
The Vietnamese government continuously requested an official apology from the Chinese government for its invasion of Vietnam but the Chinese government refused. After the normalisation of relations between the two countries in 1990, Vietnam officially dropped its demand for an apology.
Improved Relations after the war

After the brief and bloody war, both the Vietnamese and the Chinese government tried to mend their strained political ties. Both countries have made efforts to improve the tensed situation by showing support to each other. There is also a landmark of improved political ties by building the Hanoi-Kuming Highway.

Firstly, the Tiananmen Square Crackdown improved relations between the two communist countries as the Vietnam Government showed great support for the Chinese Government. This proved to be ironic as the Chinese officers who served in the third Indo-China war were active in suppressing the protest movements.

Secondly, the plan to build a Hanoi-Kunming Highway on December 2007 was a landmark in the Sino-Vietnamese relations. It contributed to facilitating trade and industrial cooperation between the nations.
Thirdly, both countries have since worked to improve their ties. Since 1991, the leaders and high-ranking officials of both nations have exchanged visits. China and Vietnam both recognized and supported the post-1991 government of Cambodia and supported each other's bid to join the World Trade Organization (WTO). In 1999, the secretary of the Communist Party of Vietnam visited Beijing, where along with Chinese President Jiang Zemin, he announced a "16 Word Guideline" for improved and strong bilateral relations; a Joint Statement for Comprehensive Cooperation was issued in 2000.
Vietnam and China also successfully negotiated a resolution of the disputes of the land border and maritime rights between 1999 and 2000. A joint agreement between China and ASEAN in 2002 marked out a process of peaceful resolution and guarantees against armed conflict. In 2002, Chinese President Jiang Zemin made an official visit to Vietnam, where numerous agreements were signed to expand trade and cooperation and resolve outstanding disputes.