How the Khmer Rouge Realigned the Cold War in Southeast Asia

Security concerns and past grievances proved greater than ideology.

Khmer Rouge soldiers: Credit Alan C. on Flicker

The involvement of outside powers in Southeast Asia through the second half of the 20th century was almost invariably framed through the logic of Cold War geopolitics. Freedom fighters seeking liberation for their country were generally granted the blanket generalization of being communists for fighting against the European imperial establishments. This designation created infamy in the West and frequently served the purpose of realigning domestic politics with a communist block that was sympathetic to their struggles. However, just because countries like Russia and China were sympathetic to the independence movements across Southeast Asia doesn’t mean that they were not motivated by realpolitik and a desire for their own variant of hegemony.

These political calculations became even more complex following the Sino-Soviet split in the 1960s, right as America was ramping up its involvement in Vietnam. Suddenly, instead of being a binary confrontation between the two blocks, China and the USSR were competing for influence across the communist world. As relationships within the Communist block shifted, Vietnam aligned itself closer to the USSR. Meanwhile, China supported an insurgent Khmer Rouge still in its infancy in Cambodia. This realignment would ultimately set the stage for one of the strangest partnerships of the Cold War.

Regional instability gave the Khmer Rouge their opportunity

The Second Indochina War (known as the Vietnam War in the US and the American War in Vietnam) hardly confined itself to Vietnam’s borders. What had started as a conflict for independence against the French became a civil war between competing visions for the future of Vietnam before ultimately becoming yet another destination of Cold War adventurism. As the war escalated, the North Vietnamese began moving war material to the south through Laos and Cambodia to supply its forces on what became known as the Ho Chi Minh Trail. This expansion of the conflict’s supporting infrastructure entangled Cambodia in the interests of both the North Vietnamese and the Americans.

To secure a favorable political environment in Cambodia, Vietnam supported and sought to influence the Khmer Rouge. This upstart Maoist insurgency began forming in rural Cambodia in their fight against Cambodia’s central government. Cambodia, though not communist at this point, had sought to ingratiate itself with China based on the belief that China would one day come to dominate mainland Southeast Asia. However, they also sought to cultivate a degree of balance between the competing blocks in an age-old strategy for states of the region. As part of a strategy of maintaining this relationship and countering the violations of their sovereignty from North Vietnam, Cambodia’s prime minister acquiesced to allowing the “hot pursuit” of North Vietnamese forces by the US across the border. This limited permission became the basis for Operations Menu, one of the most unjustifiable and overzealous bombing campaigns of the 20th century, as American B52s flew hundreds of sorties into Cambodia before ultimately being followed by a limited ground invasion of the border regions by American forces in 1970.

Some have claimed that US actions helped further destabilize Cambodia by galvanizing support for the Khmer Rouge among the rural population who bore the brunt of the US bombing campaign. Regardless of what extent this is true, the gradual entanglement of Cambodia in the war attracted more attention and support from the communist block. While North Vietnam initially provided significant material and combat support, China eventually became the primary benefactor of the Khmer Route. As the Sino-Soviet split continued to divide the communist world, this rivalry became stamped into the relationship between the Soviet-backed Vietnam and the Chinese-backed Cambodia.

Khmer-Viet provocations¹

The growing ideological and geopolitical divide within communism, coupled with the long-embittered rivalry between the Khmer and Viet states before the arrival of French colonialism, created a near-instant flash point within Cambodia’s power vacuum. This came in the form of anti-Vietnamese riots within the Cambodian capital of Phnom Penh following the collapse of the government in 1970, which steadily escalated to an organized campaign of persecution and dislocation of Vietnamese communities across Cambodia, culminating in cross-border raids by Khmer Rouge forces into Vietnam between 1975 and 1978.

The resulting tit-for-tat of cross-border raids and exchanges of fire hit its breaking point at the end of 1978 when Vietnam invaded Cambodia and drove the Khmer Rouge out of power. Pol Pot’s genocidal regime had gone from socialist brother to untenable neighbor. Vietnamese forces would not leave Cambodia until 1991.

The Vietnamese invasion realigns Southeast Asia

The specter of an expansionist Soviet-backed state gobbling up Southeast Asia realigned priorities and relationships across the region. In doing so, it would form new areas of cooperation between rivals that would have been unthinkable in the years prior.

Nixon’s outreach to China in 1972 is often credited with transforming the Cold War from a hair-trigger showdown between two rival blocks to a tri-actor global system dominated by Sino-Soviet-US relations. The sudden adventurism of the Soviet-backed Vietnamese, seemingly taking place in Indochina, provided the first test for this shifting global dynamic, which created an unlikely base of international support for Cambodia’s pariah regime.

Vietnam’s invasion of Cambodia prompted a military response from China in support of its partner to “teach Vietnam a lesson,” as Deng Xiaoping put it, resulting in the Sino-Vietnamese border war of 1979. In that conflict, the People’s Liberation Army (PLA) attempted an incursion across the Vietnamese border to put pressure on Hanoi. The operation did not go as planned, though, and the PLA was given a black eye and forced to withdraw by battle-hardened Vietnamese reservists tasked with guarding the border while the regular army deployed to Cambodia.

With Vietnamese forces now sharing a border with Thailand, having just gobbled up a shared neighbor, the Thai felt threatened enough to provide assistance for the Khmer Rouge, successfully rallying ASEAN members and the United States to cooperate with China in support of an anti-Vietnam coalition. This unofficial coalition supplied aid to the insurgent Khmer Rouge across the Thai border. It pushed for Vietnam’s withdrawal from Cambodia even while publicly decrying the genocidal brutality of the Khmer Rouge. Throughout this period, Chinese forces also continued regular, if limited, exchanges of fire with the Vietnamese across their shared border.

Cooperation between most of the region’s most significant players deeply isolated Vietnam, which was left with the Soviet Union as its only international partner and source of aid. Surrounded by enemies, with more than a million soldiers under arms and nearly 25% of their GDP going to defense, this isolation damaged the Vietnamese economy profoundly.² Coupled with its faltering efforts at collectivization, it was a significant driver of the country’s poverty. Furthermore, it made Vietnam highly dependent on foreign aid from the USSR and poorly positioned to weather the increasing ossification of the Soviet economy, let alone its total collapse.

This bizarre group of bedfellows persisted for the next ten years until a less hawkish prime minister, Chatichai Choonhavan, was elected in Thailand. Chatichai removed support for the Khmer Rouge and extended an olive branch to the Vietnamese. Around the same time, Vietnam was coming to terms with the failure of its collectivization policies and began seeking to open its economy up to international markets. Ultimately, this strangest of chapters of the Cold War came to a peaceful resolution with the Vietnamese withdrawal from Cambodia in 1991, months before the final collapse of its benefactor, the Soviet Union. Diplomatic normalization came quickly, first with China, followed by provisional acceptance into ASEAN in 1993, with full member status extended in 1995, the same year that diplomatic relations with the US were restored.

The foremost lesson to be drawn from this historical chapter is that despite the ideological nature of the Cold War and the post-nationalistic rhetoric of communism, realpolitik and nationalism were still the largest drivers of geopolitical decision-making within recently independent Southeast Asia as well as within communism’s two heavyweights, the USSR and PRC. Major powers such as the US and China were willing to discard Cold War orthodoxy when it served their geopolitical goals and could be made palatable to domestic populations. For Southeast Asian countries, the experience of colonialism and communism hadn’t erased the long history of competition and rivalry that predated the European arrival. That history of competitions across the region makes the period of stability in the region since the 1990s all the more striking of an accomplishment for the members of ASEAN.

1. Correction: I’ve made several updates to this section and the next to correct and clarify the timeline of events. Anti-Vietnamese violence began in 1970 instead of 1975 when the Khmer Rouge came to power. Khmer Rouge raids into Vietnam began in 1975 and continued until 1978, provoking Vietnam’s invasion of Cambodia in December 1978. Lastly, Nixon visited China in 1972 and not 1976 as originally published.

2. The book Vietnam Rising Dragon by Bill Hayton has an in-depth chapter on the costs of isolation in Vietnam following the war in Chapter 9.