Maritime security pressure and geopolitical competition

The first lens focuses heavily on maritime security pressure and the structural dynamics of major power competition. Scholars argue that increasing geopolitical competition in the South China Sea acts as a primary structural driver, propelling the convergence of strategic interests between Vietnam and the United States (Luu and Nguyen, 2023; Trinh and Ho, 2024). Analyses done by Grossman (2018; 2020) alongside Poling et al. (2021) emphasise that this strategic convergence is predominantly based on the shared objective of maintaining freedom of navigation. Specifically, Grossman (2018; 2020) underscores the critical question of whether Vietnam military capabilities can effectively stand up to assertive actions in the South China Sea, thereby driving the necessity for strategic deterrence (Poling et al., 2021). The State of Southeast Asia 2026 Survey Report reinforces this perspective by indicating that encroachments in the exclusive economic zones and continental shelves represent the greatest strategic concern for littoral states, with 51.7% agreement at the regional level and a striking 66.3% among experts in Vietnam (Lin et al., 2026). Furthermore, as Ong-Webb (2026) notes, the persistence of the South China Sea maritime dispute remains one of the most destabilising factors in the region, compelling regional actors to seek external balancing mechanisms to safeguard their territorial integrity. However, these studies rely primarily on the qualitative analysis of diplomatic discourse and historical events, without quantifying the specific impact level of this traditional security factor on defence cooperation decisions compared with other emerging variables. From the perspective of the United States, securing freedom of navigation and upholding the United Nations Convention on the Law of the Sea within exclusive economic zones constitute a foundational strategic objective. This diplomatic approach mirrors US strategies in other contested maritime domains, such as the Eastern Mediterranean, where international law serves as a primary stabilising mechanism against unilateral coercion (Ploumis, 2020).

Imperative of Defence Technology Modernisation

The second lens examines the need for modernisation of defence technology. While previous studies often emphasised traditional geopolitical variables (Hoang and Do, 2016), an extensive body of specialised analysis significantly broadens this perspective. Thayer (2018) details a continuous trajectory of force modernisation efforts within Vietnam over the past decade, shifting beyond conventional procurement. Concurrently, Abuza (2025) provides critical assessments detailing the profound transition of the Vietnam People’s Army towards comprehensive military modernisation. Furthermore, Burgess (2021) underscores the indispensable role of specific branches, such as air force relations, in advancing the bilateral comprehensive partnership. Building upon these foundational military needs, recent academic literature highlights the central role of technological autonomy. Vuving (2023; 2026, p. 330) asserts that in the new era of world politics, the relationship between Vietnam and the United States has reached a new state, wherein efforts to enhance self-reliance, economic resilience, and technological cooperation play a foundational role. Aligning with this perspective, Minh et al. (2025) assert that mastering strategic technologies, such as artificial intelligence, autonomous equipment, and cyberspace security, is a mandatory requirement for building modern armed forces capable of addressing multi-domain threats. Furthermore, the political stability and economic rise of Vietnam provide the necessary domestic foundation to absorb and integrate these advanced technologies (Le, 2026). Nevertheless, there remains a distinct lack of empirical evidence to measure the priority level of the technological factor compared with traditional security pressures, leaving a gap in understanding how technology transfer needs to drive contemporary defence diplomacy.

Furthermore, the operationalisation of technology transfers is strictly governed by the US statutory frameworks, detailed comprehensively within the Security Assistance Management Manual (Defense Security Cooperation Agency [DSCA], 2020). The US Department of State (2024) oversees these overarching security and defence cooperation policies. For partner nations, translating strategic alignment into tangible military capabilities relies heavily on specific legal mechanisms, notably foreign military sales and excess defence articles. As observed in comparative international contexts, adapting and rebalancing these security cooperation programs is essential to fulfill the specific force modernisation requirements of partners operating in fast-changing geostrategic environments (Ploumis, 2018).

Non-Traditional Security and Trust-Building Mechanisms

The third lens focuses on non-traditional security challenges and the mechanisms of trust-building between former adversaries. Cooperative efforts to address climate change, conduct search and rescue operations, and particularly remediate war legacies are viewed as indispensable tools to neutralise past historical enmity and build mutual confidence (Dang and Nguyen, 2019, p. 125). A study conducted by Gammon and Phan (2024) provides a crucial demonstration of this argument by analysing how the two nations implement “strategic remembering.” The authors indicate that reshaping the meaning of war monuments and addressing war legacies is not merely a historical acknowledgement but also an active tool for peaceful diplomacy, marking a new reality in bilateral relations. These cooperative activities in non-traditional fields serve as essential stepping stones to consolidate trust before expanding into more complex and sensitive traditional security agreements.

Overall, the existing literature provides a multidimensional framework of arguments regarding the drivers propelling bilateral relations. However, the majority of these works exist as qualitative studies and examine the maritime, technological, and non-traditional factors independently. This study fills that gap by synthesising the three aforementioned variable groups into a unified quantitative model to determine the precise impact weight of each factor on the decision to promote substantive defence cooperation.

Theoretical framework

This study constructs its analytical foundation by integrating the theory of asymmetrical relations (Womack, 2008) with a meticulously operationalised small-state hedging strategy and Vietnam’s distinct defence doctrines. In an asymmetrical power structure, a smaller state manages disparities by pursuing autonomy while utilising larger partners for capacity-building. Rather than treating hedging as a generic behaviour, this research unpacks the strategy through a synthesis of fifteen distinct elements identified by leading scholars (Table 1).

Vietnam applies a sophisticated combination of these elements, heavily informed by two core national doctrines. The first is the “Four No’s” policy articulated in the 2019 National Defense White Paper. This policy mandates no military alliances, no siding with one country against another, no foreign military bases, and no using force in international relations (Ministry of National Defence, 2019, pp. 23–24). This strict policy of nonentanglement serves directly as a dominance denial and balancing mechanism within its hedging strategy (Zeberlein, 2024). Consequently, to dilute dependency and avoid great power entrapment, Vietnam has successfully diversified its strategic alignments, elevating fourteen nations to comprehensive strategic partnerships rather than exclusively aligning with the United States.

The second foundational doctrine is the dialectical principle of cooperation and struggle formalised at the Eighth Plenum of the Communist Party Central Committee in 2003 and further detailed in Resolution 28-NQ/TW in 2013. This guideline dictates that partnerships and adversities are not binary concepts. Vietnam seeks to expand friendly cooperation with partners while remaining vigilant, actively struggling against any forces infringing upon its independence, sovereignty, or territorial integrity (Pham and Nguyen, 2021). This nuanced framework perfectly explains why bilateral defence cooperation concentrates heavily on selective capacity-building and non-traditional security issues rather than rigid mutual defence treaties.

Research model and hypotheses

Building upon this theoretical foundation and a comprehensive review of reputable academic literature, the study proposes a quantitative research model comprising three independent variables impacting one dependent variable. The operationalisation process of these variables is rigorously constructed to ensure empirical validity.

Research design and data-collection procedure

This study applies a quantitative method through an expert survey. The selection of this method stems from the specific nature of defence diplomacy, where policy-making documents and strategic agreements are often highly classified, leading to a severe scarcity of public macro datasets. In this context, an expert survey provides the most feasible and reliable alternative tool to quantify strategic drivers by capturing the perceptions of individuals deeply knowledgeable about foreign policy.

The study utilises non-probability sampling combined with the snowball sampling technique. The research acknowledges the inherent limitations of this technique, particularly the risk of selection bias, as participants may tend to refer peers with similar professional backgrounds or ideological perspectives. Consequently, this study does not claim absolute statistical generalisability to the entire national population. However, in research on international relations, this is the most practical approach to reach a specialised, small-scale, and hard-to-access population, such as security policymakers. The results of the study serve as an in-depth exploratory assessment of a specific elite expert cohort.

Data was collected from 150 experts who are entirely Vietnam citizens, residing and working within Vietnam. The fundamental rationale for this sampling strategy is to capture the authentic internal perspective of the host nation regarding its foreign policy and defence modernisation. By focusing exclusively on domestic perspectives, the study illuminates the internal strategic calculus of Vietnam, providing a necessary counterbalance to analyses heavily reliant on foreign intelligence or external diplomatic viewpoints. To ensure reliability of the survey sample regarding a highly complex topic, the educational level criterion was rigorously controlled, with 86.6% of participants holding postgraduate degrees. Specifically, master’s degree accounts for 57.3% and doctorates and above account for 29.3%. In terms of professional structure, the survey sample is transparently distributed into three groups representing multidimensional domestic perspectives. Policymakers account for 34.0%, lecturers directly teaching and researching national defence and security education make up 37.3%, and analysts of domestic international relations alongside military officers comprise the remaining 28.7%.

Regarding research ethics and data security, the survey strictly adhered to the established academic protocols. All 150 respondents were provided with clear guidelines outlining the academic purpose of the research prior to participation. Informed consent was obtained under the guarantee of absolute anonymity. No sensitive personal identification information was collected. The raw dataset is securely stored in encrypted formats accessible only to the primary research team, completely mitigating any risks associated with data privacy.

Measurement instrument

The measurement instrument is a questionnaire comprising twenty-one observed variables, utilising a 5-level Likert measurement scale (ranging from 1 being strongly disagree to 5 being strongly agree). The scale structure is operationalised into three independent variable groups: maritime security pressure (five variables), the need for defence technology modernisation (five variables), and non-traditional security challenges (five variables). The dependent variable, the level of defence cooperation, is measured through six observed variables. To ensure absolute transparency of the quantitative research, the full text of the survey questionnaire is provided in detail in the Appendix of the current article.

It is crucial to note that the questionnaire employs a deductive research design. The items were not arbitrarily formulated but were strictly operationalised from established international relations theories, particularly the hedging strategy and asymmetrical relations frameworks. Translating qualitative theoretical propositions into quantifiable Likert scale statements is a standard methodological procedure to statistically test predefined hypotheses. This structured design ensures that the measurement focuses precisely on testing theoretical correlations rather than conducting exploratory qualitative interviews.

Data analysis method

All raw data was coded and processed using the open-source statistical software jamovi (The jamovi project, 2024). The analytical procedure was executed through three rigorous steps: first, reliability testing using Cronbach’s alpha (α) coefficient; second, testing convergent and discriminant validity using exploratory factor analysis; and third, applying a multivariate linear regression model to test the research hypotheses.

Demographic characteristics of the survey sample

The results of descriptive statistics in Table 2 present the structure of the 150 experts participating in the survey. Regarding gender, males account for 68.0% (102 individuals) and females account for 32.0% (forty-eight individuals). Regarding age, the sample is concentrated in groups of experts with extensive experience, specifically from 30 to 45 years old (40.7%) and from 46 to 60 years old (24.7%). The even distribution among professional groups and the overwhelming proportion of those with postgraduate degrees (86.6%) ensure a solid professional foundation for the collected data.

Reliability testing and exploratory factor analysis

The results of the Cronbach’s alpha reliability analysis show that all four measurement scales ensure a high level of internal consistency. Specifically, the maritime security pressure variable group reaches 0.882; the defence technology modernisation needs variable group reaches 0.908; the non-traditional security challenges variable group reaches 0.892; and the level of defence cooperation variable group reaches 0.912. The item-rest correlation coefficients of the observed variables are all greater than 0.3, meeting the standard for further analysis.

The exploratory factor analysis (using the minimum residual extraction method combined with a Promax rotation) shows that the Kaiser Meyer Olkin coefficient reaches 0.875. Bartlett’s test of sphericity yields a Chi-square value of 1,978 with 210 degrees of freedom (DoF), achieving a statistical significance level of p < 0.001. This result proves that the data is perfectly suitable for conducting factor structure analysis.

Multivariate linear regression analysis

A multivariate linear regression model was utilised to test impact level of all three independent variables on the dependent variable. The F-test of the model reaches a value of 48.9 (p < 0.001), affirming that the regression model fits the dataset. The adjusted R² coefficient reaches 0.491, indicating that the three independent variables explain 49.1% of the variance in the level of defence cooperation. The multicollinearity check shows that the variance inflation factor (VIF) index of the variables ranges from 1.01 to 1.02, completely ruling out the risk of multicollinearity.

The analytical results in Table 3 indicate that all three independent variables have a positive impact and are statistically significant (p < 0.001) regarding the level of defence cooperation. Among them, maritime security pressure has the largest impact level (standardised coefficient: 0.496). This is followed by the need for defence technology modernisation (standardised coefficient: 0.385). The non-traditional security challenges variable has the lowest impact level in the model but still plays a crucial role (standardised coefficient: 0.341).

The shaping role of maritime security and the comparison with alliance theories

The research results indicate that maritime security pressure is the variable with the largest impact on the cooperation decision (standardised coefficient: 0.496). This finding shows alignment with macro-data from the State of Southeast Asia 2026 Survey Report, in which 66.3% of experts in Vietnam rank the risk of encroachments in the exclusive economic zone and continental shelf as the greatest security threat (Lin et al., 2026).

When comparing this result with traditional neo-realist theories—which often predict that an increase in security pressure leads to the formation of formal military alliances—the data suggests a different trend. Through the lens of the asymmetrical relations theory proposed by Womack (2008), this cooperation can be interpreted not as a process of taking sides or allying against a third party. Instead, the smaller-scale nation tends to manage asymmetry by maintaining autonomy while utilising resources from the external major power to ensure the principle of freedom of navigation. This finding highlights the limits of linear perspectives when predicting that Vietnam is moving towards a comprehensive military alliance with the United States.

The convergence of strategic interests requires active engagement from both nations. Bilateral defence relations are firmly anchored in institutional frameworks, specifically the Memorandum of Understanding on Advancing Bilateral Defense Cooperation initiated in 2011 and updated in 2022, alongside the Joint Vision Statement on Defense Relations signed in 2015 and refreshed in 2024. In practice, the United States utilises the excess defence articles mechanism to transfer assets, such as Hamilton-class cutters. These transfers significantly bolster Vietnam civilian maritime law enforcement capabilities rather than providing direct military deterrence. Additionally, approved foreign military sales, such as T-6C Texan trainer aircraft and prospective C-130 transport aircraft, illustrate a pragmatic and highly calibrated approach to capacity-building (Nguyen, 2026). This precise calibration aligns perfectly with Vietnam’s independent foreign policy while addressing immediate maritime security pressures.

However, a critical empirical paradox emerges when comparing these survey results with actual procurement patterns. While experts identify maritime security as the paramount pressure, the United States has not transferred highly lethal combat platforms to Vietnam. Instead, cooperation relies heavily on non-traditional security issues and the transfer of law-enforcement assets, such as Hamilton-class cutters, which are designed for civilian maritime patrol rather than naval deterrence against major powers. Concurrently, Vietnam actively acquires core defence technologies and lethal weapons from other international partners, including India, Israel, South Korea, and European nations.

This apparent contradiction perfectly illustrates the operationalisation of Vietnam hedging strategy and its strict adherence to the “Four No’s” policy. While the survey accurately captures the profound internal perception of maritime threats, translating this concern into actual defence cooperation with the United States is intentionally restrained. Vietnam deliberately avoids procuring sensitive lethal weapons from Washington to prevent triggering a severe security dilemma or provoking neighbouring powers. Acquiring law-enforcement vessels allows Vietnam to protect its exclusive economic zone without crossing the threshold of military alignment. Simultaneously, diversifying lethal weapon procurement to less geopolitically polarising partners serves as an optimal indirect balancing tactic. Consequently, non-traditional security cooperation remains the most politically viable avenue to maintain the US engagement in the region.

Defence technology needs and shift in the research paradigm

One of the contributions of this study is quantifying the impact level of the defence technology modernisation needs (reaching an impact coefficient of 0.385). When compared with previous literature that limits the analysis of defence relations to traditional geopolitical frameworks or lethal weapons procurement, the quantitative results show an expansion of cooperative areas.

This finding provides empirical support for the argument provided by Vuving (2026) that bilateral relations have entered a new era, where self-reliance capacity and cooperation in advanced technology play a central role. The experts’ attention to artificial intelligence, autonomous equipment, and cyberspace security reflects an effort to diversify supply sources and master technologies. Technology cooperation can be viewed as a tool to support the military modernisation goal while maintaining safety limits in relations with neighbouring countries.

Non-traditional security: From humanitarian meaning to a strategic balancing tool

Although the non-traditional security challenge has the lowest impact weight in the model (0.341), this variable maintains statistical significance (p < 0.001). Previously, some studies often evaluated non-traditional cooperation primarily in humanitarian aspects. However, when comparing the statistical results with the concept of “strategic remembering” discussed by Gammon and Phan (2024), a more multidimensional strategic perspective is presented.

The authors suggest that jointly resolving war legacies not only addresses past issues but is also utilised as a diplomatic tool to guide the future. The quantitative data of the study supports this argument: in the context where differences in political viewpoints persist, less sensitive areas, such as search and rescue, military medicine, and particularly war legacy remediation, act as a trust-building mechanism. They serve as strategic stepping stones, providing a basis to maintain regular presence of the United States in the region, creating interaction space before advancing to more extensive security agreements.

Research implications and limitations

Regarding theoretical implications, this study contributes to establishing an operationalisation process of the “hedging strategy” concept into measurable variables. Practically, comparing the driver weights assists policymakers in interpreting why the contents of the comprehensive strategic partnership focus on dual-use technology transfer and enhancing maritime law enforcement capacity rather than mutual defence commitments.

The process of interpreting the results also requires considering certain limitations. The snowball sampling method may contain risks of selection bias, although the sample was controlled with a high percentage of experts holding postgraduate degrees. Furthermore, the adjusted R² coefficient reaches 0.491, indicating that the model explains 49.1% of variance in the dependent variable. This implies that the remaining 50.9% of variance is subjected to the impact of variables not included in the model, such as differences in ideological value systems or the impacts of polarisation in global power competition. Future studies can continue to expand to evaluate the structure of this complex relationship more comprehensively.