China’s ‘Ironclad Friendship’ With Cambodia Under Test: What The Border Conflict With Thailand Reveals

Cambodia should treat Chinese friendship as a partnership, not a security guarantee, and strengthen diversification, bargaining leverage and strategic autonomy.

Analysis

On July 24, 2025, artillery, rockets, and airstrikes commenced along the Cambodia-Thailand border, marking the resurgence of a territorial dispute that has been simmering for years. It was a test of Cambodia’s most celebrated external relationship, its “ironclad friendship” with China, which it had subject to scrutiny.

The test became more severe when fighting resumed in December. By the time Cambodia and Thailand agreed to a new ceasefire on Dec. 27, the renewed conflict had lasted 20 days, killed at least 101 people and displaced more than half a million, according to Reuters. Yet Beijing neither endorsed Cambodia’s territorial claims nor condemned Thailand. It called both countries friendly neighbors, formally took a neutral stance and maintained political and military relations with Bangkok. The crisis brought a more difficult question: What is the value of ironclad friendship when it is in conflictual with the greater interests of China?​ 

Beijing’s diplomatic rhetoric of friendship is subordinate to the national interest. Cambodia is still valuable as it provides political alignment, strategic access, and diplomatic support. Thailand, however, is more economically significant, more influential in mainland Southeast Asia and has a significant defense relationship with China. Cambodia’s rhetorical status was not enough to secure exceptional Chinese support when the relationships came into tension. 

Friendship as an Instrument of Interest

The realist theory is a good starting point. When it comes to security and material gain, major powers build allies but do not let sentiment get in the way. For Morgenthau, national interest is the basis for state action, defined by power calculations; for Mearsheimer, uncertainty and self-help are the driving forces behind governments that secure freedom of action, not loyalty to weaker partners (Mearsheimer, 2001; Morgenthau et al., 2006). China’s actions are in line with this logic. Friendship is a political tool, but not an independent check on Beijing.

The recent study of the ironclad label reinforces this interpretation. Sovinda Po and Christopher Primiano have examined then-Prime Minister Hun Sen’s 2019 assertion that Cambodia and China are “ironclad friends.” They cited regime-security concerns, economic benefits, external threats, and the lack of effectiveness of ASEAN as the reasons behind Cambodia’s alignment (Po & Primiano, 2020). These are all reasons why Phnom Penh needs Beijing. They do not explain why Beijing would have to sustain serious costs to defend Cambodia. In this respect, the label reveals Cambodia’s dependency more apparent than China’s obligation.

However, Beijing did deepen bilateral relations following the conflict. In April 2026, the first “2+2” dialogue between China and Cambodia was held by their foreign and defense ministers. In June, Xi Jinping offered a bilateral security partnership and in a subsequent speech stated that the friendship had “stood the test of time and weathered storms.” This is proof that Cambodia is still a strategic asset. Yet, none of these efforts established a mutual-defense obligation or gave priority to Cambodian claims over Thai interests. Beijing managed to secure Phnom Penh’s trust and maintain influence at a relatively low cost by its institutional deepening.

Research on China’s partnership diplomacy draws a comparable conclusion. With Chinese partnerships, cooperation is institutionalized, but without automatic military obligation and entrapment in a partner’s conflicts (Strüver, 2017). From Beijing’s point of view, their flexibility is not a flaw but rather a greatest strength of their advantageous position.

China’s rhetoric toward Thailand also undermines the notion that “ironclad language” means an exclusive relationship. In 2025, at the 50th anniversary of the establishment of diplomatic relations, Xi expressed that “China and Thailand are as close as one family”. Cambodia is an ironclad friend, while Thailand is family. Consequently, Beijing can offer diplomatic generosity, as such words do not preclude its options.

Neutrality Exposed the Hierarchy

On the first day of the major clashes, China’s Foreign Ministry called Cambodia and Thailand friendly neighbors, and urged them to restraint and announced its stance as a “just and impartial position”. Later, China backed the ASEAN-led diplomacy efforts, hosted representatives of both countries and dispatched a special envoy to Phnom Penh and Bangkok during the escalation in December. 

China’s primary objective was not adjudication, but rather conflict management. It encouraged a ceasefire, humanitarian relief, demining and an ASEAN observer role, but did not validate Cambodia’s historical or legal claims. Xi’s foreign policy was meticulously symmetrical. On July 17, 2026, he met with Hun Manet and reaffirmed the ironclad friendship and supported negotiation. During the meeting with Thai Prime Minister Anutin Charnvirakul on the same day, Xi pledged to be a reliable and trustworthy strategic cooperative partner and reiterated support for peaceful dialogue.

Neutral mediation was a responsible diplomacy and helped to avoid escalation. However, it also provided the core empirical test for analysis. There was no exceptional Chinese support when Cambodia faced a more materially challenging situation as a result of a relationship that was publicly described as exceptional. For conflict management, Beijing treated its ironclad friend and its Thai partner as political equivalents.

Beijing was concerned about the potential for turmoil in mainland Southeast Asia, the protection of investments and supply routes for both nations, the preservation of its access to Bangkok and the discouragement of external powers from expanding the conflict into a broader geopolitical contest. Supporting Cambodia would have endangered these larger interests. Being neutral would have left a partner who was dependent on him with few viable options. In the eyes of the Chinese, neutrality was thus the lower cost choices.

Chinese neutrality is not the only way to demonstrate that Thailand is more important in all policy domains. Beyond to trade, the evidence of defense and diplomacy suggests that Cambodian friendship was not worth the opportunity costs of alienating Thailand. The crisis did not reveal that China had violated the agreement. It proved that the ironclad formula never limited the choice of the China.

Thailand’s Material Weight Is Greater

The most evident manifestation of inequality is in the realm of trade. In 2025, the volume of trade between China and Thailand amounted to approximately USD 147.3 billion, while the trade volume between China and Cambodia was approximately USD 19.73 billion. Notably, the absolute magnitude of the Thai-American relationship was approximately seven and a half times greater. Consequently, a disruption in trade relations with Thailand would pose a significantly higher risk to trade, business, and supply chain operations.

It is clear that Thailand’s economy was more than 11 times larger than Cambodia’s in 2025, according to World Bank data. Market size is part of the difference in trade. But this does not cancel out the hierarchy, the size of the market is one of the things that underpins it. The absolute amount of economic losses is the answer to which governments make strategic choices, not whether two small countries trade at a similar rate of GDP with China.

Cambodia’s bargaining position is further weakened by its trade structure. in 2025, Cambodia’s imports from China totaled $18.04 billion, while its exports to China totaled just $1.68 billion, according to Cambodian customs data. This resulted in a substantial trade deficit of about $16.36 billion. Furthermore, only 8.5 percent of the bilateral trade was made up of Cambodian exports. In the context of asymmetric interdependence as Keohane and Nye (2012) noted that the more dependent party bears higher costs from disruption and therefore possesses less leverage. Therefore, Phnom Penh’s continued access to Chinese markets, finance, and imports are critical to its economic well-being, but Beijing’s reliance on the Cambodian market is relatively less important.

In addition, Thailand also has a well-developed manufacturing network, a large domestic market, strategic position on major transport corridors, and a longstanding alliance with the United States. Meanwhile, Cambodia is an unusually close party-to-party ties, supporting Beijing’s key diplomatic positions, the Belt and Road projects, and the expansion of Chinese security access to the Gulf of Thailand. Furthermore, Cambodia is strategically useful due to the Chinese-funded expansion of the Ream naval base, the frequent visits by Chinese naval vessels, and the large Golden Dragon military exercise with China.

However, usefulness is not equivalent to leverage. Cambodia’s value is largely based on its willingness to conform to China, and its capacity to threaten defection is constrained by its economic and political reliance. Thailand has more options, more power and a higher capacity to impose opportunity costs on Beijing. China may prefer to keep both partners, but if their interests clash, the evidence indicates that Thailand is more difficult to disregard. 

Military Ties Precede Loyalty

The material hierarchy is reinforced by defense relations. According to the Stockholm International Peace Research Institute (SIPRI), Thailand was the third-largest recipient of Chinese major arms between 2021 and 2025, accounting for 4.7% of China’s exports. During that time, 49% of Thailand’s arms imports came from China, while 15% came from the United States. The figures should be interpreted with caution. The SIPRI trend-indicator values reflect transferred military capability, rather than contract prices or export revenues. They are unable to calculate the amount of dollars that China made from Thailand. They do indicate that Bangkok plays a significant role in China’s arms transfer network and that Chinese systems have become a significant element of the Thai defense planning process.

Certain programs are scheduled at the right times. The troubled S26T submarine project in Thailand dates back to 2017 and is estimated to cost about $400 million. The contract was not a new wartime purchase but was changed in August 2025 by the Thai Cabinet to accept a Chinese engine after Germany refused to supply the original engine. Despite the first border fight, China and Thailand continued their Falcon Strike air exercise in September 2025 and Beijing announced a 9th exercise in August 2026. This is proved that Beijing had no intention to halt or downgrade military ties with Thailand to show its support for Cambodia. However, China also continued to have arms cooperation, exercises and institutional defense relations with Cambodia. In July 2026, Thailand expressed concerns about the reported acquisition of 39 Chinese tanks by Cambodia, and Beijing responded that its defense cooperation with both nations was normal and did not involve a third party. China was also a security ally to Cambodia, a major arms supplier to Thailand and a mediator between them.

Beijing’s provision of military assistance to both sides does not substantiate military support to Thailand in the border dispute. It reveals a deeper issue, as supplier loyalty was absent. The ironclad status of Cambodia did not result in exclusivity or restraint in China’s relationship with Bangkok. This message is concerning for Phnom Penh. While Chinese arms can enhance the capacity of the Cambodians, they cannot guarantee Chinese loyalty, particularly if Beijing’s ties with the other country are more commercially and strategically advantageous. 

Cambodia Needs Strategic Insurance

The policy lesson is not just that China is not to be trusted. The greater mistake of Phnom Penh would be to treat diplomatic accolades as a strategic assurance. Po and Primiano cautioned against over-dependence, which would limit Cambodia’s autonomy (Po & Primiano, 2020). The Sino-Cambodian patron-client relationship was also studied by Ciorciari, who found important constraints (Ciorciari, 2015). Cambodia’s ties with China will remain pivotal in the areas of infrastructure, trade and defense modernization and should be maintained. It would be costly and unneeded to abruptly balance. Calibrated diversification provides more credible strategic insurance. From an economic perspective, Phnom Penh should assess the ties based on the domestic benefits rather than on the basis of the trade. Market access, logistics and investment to transfer skills should be given priority in negotiations. The trade imbalance needs to be reduced to boost Cambodia’s negotiation leverage.

In the field of security affairs Cambodia needs to further diversification deepen practical cooperation with other countries such as Japan, the United States, South Korea, India, European partners and ASEAN members. The lifting of Washington’s arms embargo in November 2025 created opportunities for military training, demining, humanitarian assistance and maritime cooperation. A wider port access at Ream Naval Base would make Cambodia’s nonexclusive policy more credible. Finally, no single external power can replace for reliable mechanisms to deal with Thailand. The danger of renewed escalation would be lessened with permanent military hotlines, regular border commissions, joint demining and verifiable reporting of incidents and ongoing ASEAN observation. Chinese mediation can assist these instruments, but cannot replace them.

Interest Is the Real Ironclad Principle

The border crisis was a practical test of ironclad friend. China has not abandoned Cambodia and it has not let friendship determine its interests. China maintained political and military relations with both sides, and the higher cost of Thailand made it difficult to prioritize Phnom Penh.

The commercial scale, regional position and defense relationship of Thailand were more important than Cambodia’s rhetorical status. Beijing’s subsequent attempts to pacify Cambodia do not overturn this assumption because it maintained a beneficial, but highly asymmetric relationship with Cambodia without limiting China’s strategic options.

The real principle of the Chinese ironclad is the protection of national interest. Therefore, Cambodia should consider friendship as a diplomatic instrument rather than an insurance against territorial loss. Strategic autonomy necessitates Phnom Penh to distinguish between praise and obligation, minimize dependence and establish alternatives options that are not based on the affection of another state.

References:

Ciorciari, J. D. (2015). A Chinese model for patron-client relations? The Sino-Cambodian partnership. International Relations of the Asia-Pacific, 15(2), 245–278. https://doi.org/10.1093/irap/lcu021

Keohane, R. O., & Nye, J. S. (2012). Power and interdependence (4th ed.). Longman.

Mearsheimer, J. J. (2001). The tragedy of great power politics. W. W. Norton.

Morgenthau, H. J., Thompson, K. W., & Clinton, W. D. (2006). Politics among nations: The struggle for power and peace (7th ed.). McGraw-Hill.

Po, S., & Primiano, C. B. (2020). An “ironclad friend”: Explaining Cambodia’s bandwagoning policy towards China. Journal of Current Southeast Asian Affairs, 39(3), 444–464. https://doi.org/10.1177/1868103420901879

Strüver, G. (2017). China’s partnership diplomacy: International alignment based on interests or ideology. The Chinese Journal of International Politics, 10(1), 31–65. https://doi.org/10.1093/cjip/pow015

Pen & Ink by: Channtha So  (The author is a Ph.D. Candidate in International Relations at The University of Cambodia and a Research Fellow at the Cambodian Institute for Cooperation and Peace (CICP). His research focuses on small state security, Southeast Asian geopolitics, and Cambodia-U.S. relations in post-Cold War era.)

>> Source: eurasiareview