Sino-Vietnamese War: The People's Liberation Army crosses the border back into China, ends the war.

The People's Liberation Army (PLA) is the principal military force of the People's Republic of China and the armed wing of the Chinese Communist Party (CCP). The PLA consists of five service branches: the Ground Force, Navy, Air Force, Rocket Force, and Strategic Support Force. It is under the leadership of the Central Military Commission (CMC) with its chairman as commander-in-chief.The PLA can trace its origins during the republican era to the left-wing units of the National Revolutionary Army (NRA) of the Kuomintang (KMT) when they broke away on 1 August 1927 in an uprising against the nationalist government as the Chinese Red Army before being reintegrated into the NRA as units of New Fourth Army and Eighth Route Army during the Second Sino-Japanese War. The two NRA communist units were reconstituted into the PLA on 10 October 1947.A majority of military units around the country are assigned to one of five theater commands by geographical location. The PLA is the world's largest military force (not including paramilitary or reserve forces) and constitutes the second largest defense budget in the world. It is also one of the fastest modernizing militaries in the world, and has been termed as a potential military superpower, with significant regional defense and rising global power projection capabilities.PRC law explicitly asserts the leadership of the CCP over the armed forces of China and designates the CMC as the nationwide military command of the People's Republic of China. The Party CMC operates under the name of the State CMC for legal and governmental functions and as the ceremonial Ministry of National Defense (MoD) for diplomatic functions. The PLA is obliged to follow the principle of the CCP's absolute civilian control of the military under the doctrine of "the party commands the gun" (Chinese: ; pinyin: Dng zhhu qing) In this sense, the PLA is not a national army of the type of traditional nation-states, but a political army or the armed branch of the CCP itself since its allegiance is to the party only and not the state or any constitution. At present, the Chairman of the Central Military Commission is customarily also the General Secretary of the Chinese Communist Party.Since 1949, China has used nine different military strategies, which the PLA calls "strategic guidelines". The most important came in 1956, 1980, and 1993. In times of national emergency, the People's Armed Police (PAP) and the China Militia act as a reserve and support element for the PLAGF. Politically, the PLA is represented in the National People's Congress with 294 deputies, all of whom are CCP members.

The Sino-Vietnamese War (also known by various other names) was a border war fought between China and Vietnam in early 1979. China launched an offensive in response to Vietnam's actions against the Khmer Rouge in 1978, which ended the rule of the Chinese-backed Khmer Rouge. Both China and Vietnam claimed victory in the last of the Indochina Wars.

Chinese forces invaded northern Vietnam and captured several cities near the border. On 6 March 1979, China declared that the gate to Hanoi was open and that their punitive mission had been achieved. Chinese troops then withdrew from Vietnam. As Vietnamese troops remained in Cambodia until 1989, China was unsuccessful in its goal of dissuading Vietnam from involvement in Cambodia. Following the dissolution of the Soviet Union in 1991, the Sino-Vietnamese border was finalized. Although unable to deter Vietnam from ousting Pol Pot from Cambodia, China demonstrated that its Cold War communist adversary, the Soviet Union, was unable to protect its Vietnamese ally.