The fierce crackdown launched by former Prime Minister Hun Sen in Cambodia against critics of the Cambodia-Laos-Vietnam Development Triangle Area (CLV-DTA) has deep historical roots.

The CLV-DTA, which covers 13 provinces in Cambodia, Vietnam, and Laos, was established in 2004. The agreement is framed in an apparently innocuous way, with aims such as cooperation in socio-economic development, defense, and security. For much of its existence, it has drawn little direct political attention, though independent researchers have found that most of the benefits of the agreement accrue to Vietnam.

Cambodia plans to host a summit on the progress of the triangle later this year. The issue came to life on July 23, when Hun Sen, now president of the Senate, took to Facebook to announce that three people had been arrested for spreading false information about the agreement.

Hun Sen handed over the office of prime minister to his son Hun Manet in August 2023, though he has made it clear that he is still in charge. In his Facebook broadcast, Hun Sen took particular exception to claims that the CLV-DTA was initially proposed by Vietnam, and called for severe penalties against anyone suggesting that the agreement involved a loss of Cambodian sovereignty.

His comments provoked large-scale protests throughout the global Cambodian diaspora, and more criticism of the agreement on social media inside the country. It is hard to imagine that Hun Sen did not anticipate these consequences. Between late July and August 28, according to Amnesty International, at least 94 people were arrested for publicly criticizing the CLV-DTA, some of them children. Other schoolchildren, meanwhile, were mobilized to chant their support for the agreement in set-piece videos.

This extreme sensitivity, and Hun Sen’s need to engage in managed provocation to try and flush out the dissidents, can only be understood in a long-term historical context. Anything which suggests that Cambodia is losing territory or sovereignty to Vietnam has the potential to result in mass political mobilization. According to David Chandler in his “A History of Cambodia,” the pre-colonial Cambodian polity was weakened in the second half of the seventeenth century as its eastern maritime access was curtailed by Vietnamese expansion, as well as the increasing influence of Chinese merchants.

Cambodia became a weakened polity, obliged to pay tribute to both of its more powerful neighbors, Thailand, then called Siam, to the west, and Vietnam to the east. Internal instability was one result. Competing court factions in Cambodia would rely on either Siamese or Vietnamese backing, and defeated factions would seek support from the other side.

The system had a certain stability in the eighteenth century, but was not isolated from external factors. Siam suffered a heavy military defeat at the hands of Burma in 1767, in which the capital Ayutthaya was destroyed. This put a heavy strain on Siam’s relationship with Cambodia, as the need to extract labor power and military forces from Cambodia became more acute. In 1783, about 10,000 Khmers were levied to build a city wall for the new capital of Bangkok, and Siamese raids in the early nineteenth century in search of manpower led to a decrease in Cambodia’s population.

Students of colonialism often fall into the trap of believing that European colonialism was the only game in town. In many parts of the world, local colonialisms were at work when the Europeans arrived. While Siam’s primary concern in Cambodia was to secure labor power, Vietnam, which had very scarce land resources, aimed to extend its centuries-old process of territorial expansion to the south. Attempts by the Cambodian court to escape tribute obligations to Siam pushed it into the arms of Vietnam. This was a case of jumping out of the frying pan and into the fire. Vietnam and Siam fought for control of Cambodia for 14 years from 1833, part of a period that Chandler describes as the darkest in Cambodian history prior to the Khmer Rouge. The image of Cambodians buried up to their necks by their Vietnamese masters who then boiled pots of tea balanced on their heads remains embedded in the national consciousness.

France established a protectorate over Cambodia in 1863, both in response to the brutal persecution of French missionaries in Vietnam, and as a way of extending its commercial interests in the region. The protectorate was a step towards the French conquest of Vietnam. Within the aggregated colony of Indochina, which also included Laos, the Vietnamese were seen as the most promising population, and the bulk of French colonial resources spent on “civilizing” the region were used for Vietnamese development.

Cambodia’s Kampuchea Krom provinces were handed over to Vietnam by France in 1949. Today, the Khmer Krom community in Vietnam consists of about 1.2 million people. Even within the narrow confines of Cambodian political discussion, their plight draws little attention. A report in April by the Unrepresented Nations and Peoples Organization (UNPO) found that the Khmer Krom in Vietnam remain subject to persecution and arbitrary arrest. The Khmer Krom, the UNPO has found, are unable to openly study their native language, while those who have returned to Cambodia face social and economic discrimination as they are often perceived as being Vietnamese.

Hun Sen’s personal sensitivity to any suggestion that Cambodian sovereignty is being ceded to Vietnam has to be understood in terms of his own background. He joined the Khmer Rouge in 1970, during the U.S. bombing of Vietnamese communist redoubts in eastern Cambodia. Hun Sen then defected to Vietnam in 1977, two years after the Khmer Rouge came to power. His Cambodian regime was installed by the Vietnamese invasion of 1979, and Vietnamese troops did not officially leave the country until 1989. The political connections between the Cambodian People’s Party and its counterpart in Hanoi have since remained close.

There are few borders anywhere in the world where the exact physical demarcation of the border is as sensitive an issue as the border between Cambodia and Vietnam. Opposition leader Sam Rainsy immediately left Cambodia after having attended a symbolic removal of a handful of border posts by villagers in Svay Rieng province in 2009, and it wasn’t until 2013 before he was allowed back. The journalist Chhay Sophal, who was allowed access to Hun Sen and his wife Bun Rany to write books about them, devoted a whole book to demonstrating that the border posts between Cambodia and Vietnam were in the correct places.

The Hun Sen regime has to an extent pivoted away from its early reliance on Vietnam, and now counts China as its major international ally. In financial and military terms, China provides much more support for Cambodia than Vietnam. Yet as the CLV-DTA protests show, the regime’s Vietnamese roots remain an overriding political issue in the eyes of many Cambodians.

One day there will be a government in Cambodia that is not based on the Hun family power. Whether that happens in the short term or in the distant future, a fundamental challenge for the new government will be to avoid cementing its legitimacy by allowing reprisals to be carried out against the Vietnamese in Cambodia.