Vietnam War

==Involvement of other countries==
{{main|International participation in the Vietnam War}}

===Pro-Hanoi===
====China====
{{See also|China in the Vietnam War}}The People's Republic of China provided significant support for North Vietnam when the U.S. started to intervene, included through financial aid and the deployment of hundreds of thousands of military personnel in support roles. China said that its military and economic aid to North Vietnam and the Viet Cong totaled $20&nbsp;billion (approx. $160&nbsp;billion adjusted for inflation in 2022) during the Vietnam War;<ref name="Womack" />{{Rp|}} included in that aid were donations of 5&nbsp;million tons of food to North Vietnam (equivalent to North Vietnamese food production in a single year), accounting for 10–15% of the North Vietnamese food supply by the 1970s.<ref name="Womack" />{{Rp|}}

In the summer of 1962, [[Mao Zedong]] agreed to supply Hanoi with 90,000 rifles and guns free of charge, and starting in 1965, China began sending [[Anti-aircraft warfare|anti-aircraft]] units and engineering battalions to North Vietnam to repair the damage caused by American bombing. In particular, they helped man anti-aircraft batteries, rebuild roads and railroads, transport supplies, and perform other engineering works. This freed North Vietnamese army units for combat in the South. China sent 320,000 troops and annual arms shipments worth $180&nbsp;million.<ref name="Qiang">{{Cite book |last=Qiang |first=Zhai |title=China and the Vietnam Wars, 1950–1975 |publisher=University of North Carolina Press |year=2000 |isbn=978-0-8078-4842-5}}</ref>{{Rp|135}} The Chinese military claims to have caused 38% of American air losses in the war.<ref name=Womack/>{{Rp|}}

The PRC also began financing the Khmer Rouge as a counterweight to North Vietnam at this time. China "armed and trained" the Khmer Rouge during the civil war, and continued to aid them for years afterward.<ref>{{Cite news |last=Bezlova, Antoaneta |date=21 February 2009 |title=China haunted by Khmer Rouge links |work=Asia Times |url=http://www.atimes.com/atimes/China/KB21Ad01.html |url-status=unfit |archive-url=https://web.archive.org/web/20090223174332/http://www.atimes.com/atimes/China/KB21Ad01.html |archive-date=23 February 2009}}</ref>

====Soviet Union====
{{Hatnote|For further reading, see [[Bibliography of the post-Stalinist Soviet Union]]}}
{{split section|Soviet Union and the Vietnam War|date=May 2023}}
[[File:Leonid Brezhnev and Richard Nixon talks in 1973.png|thumb|[[Leonid Brezhnev]] (left) was the Soviet Union's [[Leaders of the Soviet Union|leader]] during the Vietnam War.]]
[[File:Учителя и ученики. Фото, сделанное весной 1965 г. в зенитно-ракетном учебном центре во Вьетнаме.jpg|thumb|Soviet anti-air instructors and North Vietnamese crewmen in the spring of 1965 at an anti-aircraft training center in Vietnam]]

The Soviet Union supplied North Vietnam with medical supplies, arms, tanks, planes, helicopters, artillery, anti-aircraft missiles and other military equipment. Soviet crews fired Soviet-made [[surface-to-air missile]]s at U.S. aircraft in 1965.<ref>{{cite news|newspaper=The New York Times|title=Russians Acknowledge a Combat Role in Vietnam|date=14 April 1989|page=13|url=https://www.nytimes.com/1989/04/14/world/russians-acknowledge-a-combat-role-in-vietnam.html#:~:text=Soviet%20soldiers%20sent%20to%20the,Soviet%20Army%20newspaper%20reported%20today|archiveurl=https://web.archive.org/web/20230407114837/https://www.nytimes.com/1989/04/14/world/russians-acknowledge-a-combat-role-in-vietnam.html|archive-date=April 7, 2023}}</ref> Over a dozen Soviet soldiers died in this conflict. Following the [[dissolution of the Soviet Union]] in 1991, [[Russia|Russian Federation]] officials acknowledged that the USSR had stationed up to 3,000 troops in Vietnam during the war.<ref>{{Cite news |title=Soviet Involvement in the Vietnam War |publisher=historicaltextarchive.com |agency=Associated Press |url=http://historicaltextarchive.com/sections.php?action=read&artid=180|archiveurl=https://web.archive.org/web/20120222024941/http://historicaltextarchive.com/sections.php?action=read&artid=180|archive-date=February 22, 2012}}</ref>

According to Russian sources, between 1953 and 1991, the hardware donated by the Soviet Union included: 2,000 tanks; 1,700 [[Armoured personnel carrier|APCs]]; 7,000 artillery guns; over 5,000 anti-aircraft guns; 158 surface-to-air missile launchers; and 120 helicopters. In total, the Soviets sent North Vietnam annual arms shipments worth $450&nbsp;million.<ref>{{Cite book |last1=Sarin |first1=Oleg |url=https://archive.org/details/alienwarssovietu00sari |title=Alien Wars: The Soviet Union's Aggressions Against the World, 1919 to 1989 |last2=Dvoretsky |first2=Lev |publisher=Presidio Press |year=1996 |isbn=978-0-89141-421-6 |pages=[https://archive.org/details/alienwarssovietu00sari/page/93 93–4] |url-access=registration}}</ref><ref name="Hastings" />{{Rp|364–371}} From July 1965 to the end of 1974, fighting in Vietnam was observed by some 6,500 officers and generals, as well as more than 4,500 soldiers and sergeants of the [[Soviet Armed Forces]], amounting to roughly 11,000 military personnel.<ref>{{Cite web |title=Soviet rocketeer: After our arrival in Vietnam, American pilots refused to fly |url=http://rus.ruvr.ru/2010/01/29/3985810.html |url-status=dead |archive-url=https://web.archive.org/web/20130117082418/http://rus.ruvr.ru/2010/01/29/3985810.html |archive-date=17 January 2013 |access-date=26 May 2010 |publisher=rus.ruvr |language=ru}}</ref> The [[KGB]] had also helped develop the [[signals intelligence]] capabilities of the North Vietnamese, through an operation known as Vostok (named after the [[Vostok 1]]).<ref name="MP">{{Cite web |last=Pribbenow |first=Merle |date=December 2014 |title=The Soviet-Vietnamese Intelligence Relationship during the Vietnam War: Cooperation and Conflict |url=https://www.wilsoncenter.org/sites/default/files/CWIHP_Working_Paper_73_Soviet-Vietnamese_Intelligence_Relationship_Vietnam_War_0.pdf |url-status=dead |archive-url=https://web.archive.org/web/20190412060039/https://www.wilsoncenter.org/sites/default/files/CWIHP_Working_Paper_73_Soviet-Vietnamese_Intelligence_Relationship_Vietnam_War_0.pdf |archive-date=12 April 2019 |access-date=1 June 2018}}</ref>

===Pro-Saigon===
{{See also|Southeast Asia Treaty Organization|Many Flags}}
As South Vietnam was formally part of a military alliance with the US, Australia, New Zealand, France, the United Kingdom, Pakistan, Thailand and the Philippines, the alliance was invoked during the war. The UK, France and Pakistan declined to participate, and South Korea, Taiwan, and Spain were non-treaty participants.