Third ICW
Theme III: The Cold War and Southeast Asia (1945-1991)
Topic: The Outbreak of the Third Indochina War (1978)
Questions to Guide Understanding:
Why did the Third Indochina War break out in 1978?
Overview of the Outbreak of the Third Indochina War (1978)
The Third Indochina War ignited in 1978 when Vietnam invaded Cambodia. This invasion aimed to overthrow the pro-China regime known as Democratic Kampuchea (DK) and to establish the People’s Republic of Kampuchea (PRK), a government aligned with Vietnam. The primary impetus for Vietnam’s incursion was to halt the DK’s genocidal actions, which had led to widespread suffering among the Cambodian populace. However, this military intervention rapidly escalated into a broader regional conflict. Vietnam, supported by the Soviet Union, found itself in direct confrontation with the DK regime, which was heavily backed by China—Vietnam’s historical rival. In direct retaliation for the invasion, China launched a military attack on Vietnam in 1979, marking a significant escalation in hostilities. Vietnam maintained a military presence in Cambodia for the next decade, leading to ongoing skirmishes and a conflict that persisted until 1991. This war was unprecedented as it represented the first direct military confrontation between communist nations since the Soviet and Chinese communists had collaborated against the United States during the Vietnam War. The outbreak of this war led to a complete upheaval of previous alliances, complicating the geopolitics of Southeast Asia and necessitating a reevaluation of allegiances and hostilities in the region. The war's multifaceted origins include long-standing historical animosities, provocations by the DK, and the broader context of the Sino-Soviet split, which influenced the motivations of both Vietnam and China. A pivotal moment in this conflict occurred in January 1979 when Vietnamese forces entered Phnom Penh, significantly altering the power dynamics in the region.
Background: Understanding the Khmer Rouge
2.1. The Origins of the Khmer Rouge
The Khmer Rouge, which ruled Cambodia from 1975 to 1979, emerged from a complex historical backdrop involving colonial rule and a rise in nationalism. The roots of this movement can be traced back to broader communist movements in French Indochina, which were fueled by widespread resentment towards the oppressive French colonial administration. In 1930, the revolutionary Ho Chi Minh unified various smaller communist factions in Vietnam under the Communist Party of Vietnam, later referred to as the Indochinese Communist Party (ICP), which sought to include Cambodian and Laotian revolutionaries in its fold. Following World War II, the political landscape shifted dramatically as French colonial authority weakened, particularly after the decisive Viet Minh victory at Dien Bien Phu in 1954. The Geneva Accords recognized Cambodia as an independent entity; however, the resulting political vacuum was filled by ultranationalist communists, many of whom were radicalized during their studies in France, including Pol Pot, who became a significant figure in the Khmer Rouge.
2.2. Cambodian Politics and the Khmer Rouge’s Path to Power (1955-1975)
During King Norodom Sihanouk’s reign, Cambodia faced significant challenges in maintaining neutrality amid the intensifying Vietnam War. Sihanouk attempted to balance relations with both the United States and the communist bloc, which became increasingly untenable as US involvement deepened. His eventual break with the US and covert support for North Vietnamese operations in Cambodia compounded tensions and paved the way for the Khmer Rouge's rise to power. In March 1970, during a search for external support against domestic opposition led by General Lon Nol, Sihanouk was deposed in a coup. This coup drastically altered the political landscape of Cambodia. The following civil war saw the Khmer Rouge, energized by popular support for Sihanouk and resentment towards Lon Nol's pro-US stance, seize control and fundamentally reshape Cambodian governance based on radical communist ideology. This culminated on April 17, 1975, when the Khmer Rouge captured Phnom Penh, effectively ending the monarchy.
2.3. The Khmer Rouge in Power (1975-1979)
Upon seizing power, the Khmer Rouge enacted radical social and political changes, dismantling traditional societal structures, curtailing civil liberties, and abolishing economic systems in favor of agrarian communes. The regime’s rule quickly devolved into brutality, characterized by severe purges targeting perceived enemies and genocidal policies that precipitated widespread famine and suffering. Estimates suggest that the death toll during this period reached between 1.5 and 3 million due to a combination of economic mismanagement, oppression, and starvation.
The Local Genesis of the Third Indochina War
3.1. Historical Animosities between the Khmer and Vietnamese Peoples
The historical tensions between Cambodians and Vietnamese, marked by territorial conflicts and a history of Vietnamese expansionism into Cambodia, significantly fueled the antagonisms that ignited the Third Indochina War. These centuries of interaction cultivated a deep-seated resentment among the Khmer people, often aggravated by the policies enacted by the Vietnamese state, which frequently resulted in the loss of Cambodian land and territory.
Southward Expansion of Viet: After shaking off centuries of Chinese colonial rule in the tenth century, the Vietnamese began to expand south and this came at the expense of other peoples, including the Khmers. However, in 1834, emperor Minh Mangcame to power as a strong believer in creating a modern, centralised Vietnamese state, especially in the face of the expansion of European colonialism into the region. Minh Manh instituted direct rule in eastern Cambodia, turning it into a province of Vietnam. This lasted until 1848 when Cambodia reasserted its independence following a Cambodian rebellion and Siamese intervention. Throughout their period of colonisation in the 1830s, the Vietnamese tried to impose their own culture upon the Cambodian. Thus, the Vietnamese referred to Cambodia’s civilisation as that of “border barbarians. With this attitude, the Vietnamese not only imposed their own administrators on Cambodia but also attempted to change Cambodian clothing, language, and agriculture. The Vietnamese even hoped that their Sino-Vietnamese Mahayana forms of Buddhist worship would permeate the Cambodians’ Theravada form of Buddhism. Thus, established the Vietnamese as hereditary enemies.
Cambodia’s Perceived Loss of Territory to Vietnam:
Adding to Cambodians’ historical animosity towards Vietnam was their perceived loss of Kampuchea Krom (the area of the Mekong Delta that was once lower Cambodia) to Vietnam. Prey Nokor was one of the most important commercial cities in Kampuchea Krom, but the name was first changed to Saigon and then to Ho Chi Minh City. From the early 17th century onwards, portions of Kampuchea Krom were turned over to Vietnam by Cambodian kings in exchange for Vietnamese military support and Vietnamese progressively settled in the area. Under relentless pressure, the Vietnamese court finally formally ceded three provinces of southern Vietnam to France in 1862, followed by the three westernmost ones in 1867, all of which became part of French Cochinchina.
3.2. Political Competition for Influence
Between 1970 and 1975, the relationship between the Khmer Rouge and the North Vietnamese was fraught with political rivalry as both sought to assert dominance in the region. While the Vietnamese initially supported the Khmer communists against the pro-US regime led by Lon Nol, the Khmer Rouge’s eventual rise and power grab alienated many in Vietnam, resulting in escalating hostility between the two factions.
Almost immediately after the Khmer Rouge seized power, armed clashes between Democratic Kampuchea and Vietnam erupted along their common land border and on islands in the Gulf of Thailand. The Khmer Rouge attacked Vietnamese-controlled islands in the Gulf of Thailand, claiming the islands that the French had reassigned to their former colony of Cochinchina, and which had been inherited by South Vietnam. Vietnam recaptured the islands by force and retaliated by attacking and occupying the Cambodian island of Poulo Wai. However, while ready to openly stake their territorial claims, neither revolutionary regime was willing at this stage to embark on a full-scale conflict.
Although the Khmer Rouge had purged the Khmer Viet Minh, Pol Pot and his circle continued to fear that agents of Hanoi might still be hidden within the party. After all, the Khmer Rouge leaders believed, and publicly reiterated many times, that in 1975 the Kampuchean revolutionary army alone had “defeated the American imperialists”. And their current enemy – Vietnam – was not as strong as the US. KR then restart their attacks along the land border with Vietnam to reassert their claim to territory under Vietnamese control over which Cambodia claimed sovereignty on April 1977. In December 1977, Hanoi used warplanes, artillery, and around 20,000 men in a major thrust into the “Parrot’s Beak” province of Svay Rieng, Cambodia, only 55 miles from Ho Chi Minh City. They could have easily captured the capital city and occupied all of cambodia but the purpose was just to show their capability and inflict enough damage to curb KR aggression. (No effect)
The Internationalisation of the Third Indochina War
Vietnam's invasion in 1978 must be understood within the broader international context, especially its turbulent relations with China. Although the provocations from the Khmer Rouge contributed to the decision to intervene, the combination of local animosities and significant geopolitical shifts, particularly Vietnam’s alignment with the Soviet Union, defined the undercurrents leading to armed conflict. The Vietnamese invasion was thus a strategic decision, intended to quell what they perceived as an imminent existential threat posed by a hostile Cambodia that was bolstered by Chinese support.
Strained SIno-Viet: For the Chinese, the Sino-Soviet split led Beijing to be in constant fear that Hanoi would tilt towards Moscow, given North Vietnam’s growing reliance on Soviet economic and military aid to fight the Vietnam War. For the Vietnamese, the need to maintain Soviet aid meant that Hanoi had to keep Beijing at a distance. At a much deeper, partly conscious and partly unconscious, level, Vietnamese suspicions of the Chinese were influenced by collective historical memories of Chinese domination of Vietnam.
Tet Offensive: in early April 1967, Vietnamese leaders did meet with their Chinese allies in Beijing to discuss the shift in strategy from waging protracted guerrilla warfare to launching a major offensive against the Americans. At the Beijing meeting, Chinese leaders gave their approval to the North Vietnamese. However, Beijing deemed the move premature and signalled to them that NV were moving more towards a Soviet dependent strategy.
Post Tet: Beijing’s active opposition to North Vietnam’s peace initiatives prior to 1968 and its harsh criticism following North Vietnam’s agreement to enter talks with the US vs Moscow’s active support for peace talks prior to 1968 and the Soviet Union’s role in ensuring that the Paris peace negotiations advanced past their initial hurdles. The Vietnamese saw Beijing’s advice to maintain a protracted, low-level military struggle in the south and avoid negotiations with the US as serving China’s own strategic interests.
prevent US from attacking China by busying them with Vietnam
prevent NV and SV from reuniting into a strong independent state on China’s border
strain US-Soviet detente
Hanoi ended up negotiating which China found too similar to Soviet revisionism. However, the conversations between Chinese and Vietnamese leaders at the time indicate that Beijing’s policies were motivated by disapproval and outright anger with the Vietnamese for disregarding Chinese advice.
Triangular Diplomacy:
In the post-Tet period, as the US engaged in diplomatic negotiations with North Vietnam to end the Vietnam War, it also engaged in triangular diplomacy to exploit the Sino-Soviet split to advance its position in the negotiations with North Vietnam. By 1969, Beijing began to revise its global strategy and pursue its own geostrategic interests at the expense of its relations with Hanoi. Coinciding with the shift in Beijing’s foreign policy was the Nixon’s administration’s diplomatic strategy of ending the Vietnam war on American terms by exploiting the Sino-Soviet split. Since both China and the USSR wanted to work with the US to counter-balance the other, the Nixon administration engaged in détente with the USSR and rapprochement with the PRC to get both sides to compete for America’s good favour.
Henry Kissinger, made his secret trip to the PRC in July 1971.
Following the announcement of Kissinger’s secret trip to Beijing, the Soviets moved quickly to set a date in 1972 for a Moscow Summit with the US. The Americans let the Soviets know that they were drawing the short end of the stick to incentivise the Soviets to do more to help the Americans in Vietnam.
When North Vietnamese leaders returned to Paris in January 1973 to sign the “Paris Agreement on Ending the War and Restoring Peace”, they did so because Hanoi believed that the Sino-Vietnamese alliance would no longer hold out.
The Vietnamese communist leadership deeply subscribed to an internationalist ideology that viewed the struggle against imperialism as the primary objective of all true communists. To them, unity amongst communists was thereforeparamount and a practical necessity. While the Vietnamese communists viewed the Soviet Union’s détente with the West as an acceptable compromise to strategically achieve more gains for the socialist camp in the long run, they viewed Chinese rapprochement with the West as motivated by short-term nationalist interest and was thus a “betrayal”.
Sino-Viet tension after second icw:
Increased Competition in Indochina
Following the signing of the Paris Peace Agreement, China’s fear of an Indochina under sway of Hanoi controlled by Moscow increased with the end of direct US intervention in the region. In the spring of 1974, China shifted its position from wanting a political settlement in Cambodia to support of the Khmer Rouge’s struggle, after it became increasingly clear that Pol Pot would pose a strong buffer against the North Vietnamese
Divergence in Aims
Conflicting visions both parties had of Vietnam’s struggle. China no longer wanted a unified Vietnam under the control of Hanoi, given the deterioration of Sino-Vietnamese relations and the strengthening of Soviet-Vietnamese relations.
Disagreements over Maritime and Land Boundaries
In 1973, armed clashes took place at the Sino-Vietnamese border between northern Vietnam and China’s two southern provinces and autonomous region. In addition to the land border dispute, Hanoi and Beijing disagreed over maritime boundaries. In 1973, Hanoi shifted its attention to post-war reconstruction and, in late December, informed the PRC of its intention to exploit the natural resources, by drilling for oil, in the Tonkin Gulf. Hanoi insisted on using the 1887 Sino-French convention to demarcate the boundary, but Beijing rejected this proposal since it gave DRV two thirds of the area.
Sino-Viet Tension over Viet treatment to chinese ethnic
The Vietnamese leadership came to fear the Hoa as subversive agents of the PRC and undertook a series of discriminatory measures towards them in 1976 which convinced Beijing that Hanoi wanted to pursue an anti-Chinese policy w USSR.
Amongst the measures that the Vietnamese government undertook towards the Hoa was a campaign for substituting a single Vietnamese citizenship in place of the dual citizenship. Those who refused to do so lost their national privileges and were treated as foreign resident, with higher taxes and other discriminatory measures.
In April 1978, thousands of ethnic Chinese began leaving Vietnam for China. China publicly denounced Vietnam for “ostracising, persecuting and expelling” the Hoa, sending ships to bring home the Hoa remaining in Vietnam, which Vietnam viewed as an act of aggression and a threat of further pressures from China.
Soviet-Viet Closer
From 1975 onwards, as China reduced its economic aid to pressure Vietnam to align with it against the Soviet Union, Vietnam moved towards closer economic and political cooperation with the Soviet Union.
In September 1975, the Vietnamese indicated that their goal during the visit was to improve Vietnamese-Chinese relations. In particular, they wanted to assure the Chinese that Vietnamese relations with the Soviet Union and China would remain as before, which provided little comfort. When Beijing realised that Vietnam would not side with them against the Soviet Union, it informed Vietnam that it would not be able to continue providing non-refundable aid at the 1973 level that Zhou Enlai had promised.From now on, Vietnam would have to cooperate more closely with the Soviet Union both economically and politically. In October 1975, Le Duan travelled to Moscow nd the Soviets reportedly pledged more than $3 billion to Vietnam’s five-year plan.
Yet, at this point, Vietnam still sought to maintain its independence in foreign policy and was not ready to openly join a Soviet international bloc. They continued to remain publicly neutral and refused to join the Soviet-oriented economic bloc, COMECON.
Vietnam Officially Joins COMECON (June 1978)
In May 1978, China cancelled aid to twenty-one projects in Vietnam, going on to further cancel fifty-one more projects, including the equipment and money used in them, and the recall of numerous specialists. Faced with pressure, Vietnam decided to officially join COMECON in June 1978 in order to secure more Soviet economic assistance.
The Soviet-Vietnamese Treaty of Friendship and Cooperation (November 1978)
By June 1978, the Vietnamese had planned to invade Cambodia and considered Soviet military support vital for the success of such an operation. The treaty amounted to a statement of economic and political alliance, and almost but not quite a military alliance.
The Vietnamese thoughts that by formally tying themselves to the “world socialist system” they would be compelling the Soviet Union into providing a protective shield for Vietnam. In effect, the treaty was perceived as a minimal insurance policy by the Vietnamese communists, who had already decided to launch a full-scale invasion of Cambodia at the beginning of the next dry season, only a few weeks later.
However, the soviets seem to have perceived the treaty differently. The treaty allowed for a “consult” with a view to taking “effective measures” to “eliminate the threat”. No obligation for direct military intervention was required. The Vietnamese had wanted a clear formulationof military assistance but the Soviets refused. Furthermore, soviet leaders were not informed of Vietnam’s plans to invade Cambodia.