Southeast Asia sits at the heart of a changing security landscape in the Indo-Pacific. As the U.S.-China rivalry continues to widen the gap between formal alliance structures and the practical needs of states that seek to maintain stability without binding commitments, Southeast Asian nations have made attempts to work collectively through institutions such as the Association of Southeast Asian Nations (ASEAN). These organizations help member nations maintain their core value of autonomy and build habits of cooperation that are both flexible and pragmatic. Historically, the nations of ASEAN have maintained a proclivity toward pursuing policies that protect political autonomy and avoid entanglement from external competition. However, the introduction of the Australia, U.K., and U.S. pact (AUKUS) adds a new dimension to the geopolitical calculus of the region. AUKUS promises stronger maritime deterrence and sustained U.S. engagement through the treaty’s Pillar I, which commits the U.S. to providing three American Nuclear Powered Submarines to Australia by the 2030s, bolstering defense through a new class of Australian powered nuclear submarines. While receiving a lot of attention in the media over the prospect of nuclear technology sharing to Australia, a major ASEAN partner with a significant stake in the contested Indo-Pacific region due to its strong economy and existing alliances, Pillar I of AUKUS remains a long-term goal given the pressing short-term security concerns present in the region. Pillar II of AUKUS, on the other hand, is focused on providing advanced capabilities, joint innovation, and information sharing to enhance defensive posturing in the region. By prioritizing practical technology cooperation, AUKUS seeks to strengthen the trilateral partnership between its constituent members in order to deliver usable tools and advanced capabilities at a faster rate. This approach allows for security guarantees to exist in the region without the need for mutual defense treaties, making it an appealing model for ASEAN member states to follow. A project-by-project approach based on Pillar II of AUKUS would offer a framework for future security guarantees, avoiding binding alliance obligations, and lowers the barriers to defense cooperation and investment with the U.S. This approach would further create a competitive alternative to Chinese financing and defense-linked activity by emphasizing transparency, local benefits, and maintaining sovereign control of technologies produced under this strategic framework.  

AUKUS represents a shift away from traditional collective defense models toward a form of capability-based minilateralism, in which practical defense integration and technology sharing becomes the basis of strategic partnerships, rather than formal alliance commitments. This approach is particularly relevant to Southeast Asia, where governments seek to balance their pursuit of security cooperation with the maintenance of their sovereign autonomy by avoiding perceived alignment with or against China. 

The Strategic Logic of Pillar II

AUKUS is structured around two pillars that maintain different timelines and hence will have differing strategic effects. Pillar I, which focuses on the provision of nuclear-powered attack submarines to Australia, would greatly expand the capacity of the United States and its allies to monitor maritime spaces and project power throughout the region. Nuclear-powered submarines offer superior endurance, stealth capabilities, and the ability to operate at long ranges across the Pacific. Analysts have noted that platforms of this type remain among the most survivable and valuable assets in high-threat maritime environments such as the Indo-Pacific. This aspect of AUKUS is thus vital for the long-term consequences of the regional balance of power. 

However, the acquisition and construction process of nuclear submarines is slow and complex. The timeline of this project does not anticipate the first Virginia-class submarines to enter service until the early 2030s, barring additional time and asset allocations dedicated to training crews, development of domestic maintenance infrastructure, and the integration of joint operational frameworks between the U.S. Navy and British Royal Navy. Pillar I of AUKUS therefore represents a more long-term rebalancing of power, whose effects will not be felt immediately but rather in a gradual shift.

Pillar II, by contrast, provides immediate opportunities for cooperation through the joint development of advanced defense capabilities. Conflicts in recent years have demonstrated the rising value of shared information networks, unmanned systems such as drone technology, cyber capabilities, and precision strike systems. The continued integration of unmanned systems and intelligence platforms have become central components of modern warfare which are changing the conventional understanding of deterrence. In this environment, deterrence is not only about the quantity of military assets but also the ability to integrate and coordinate the usage of assets across various domains. Pillar II of AUKUS directly responds to the shift in deterrence by establishing research channels, cooperating on the development of new technologies, and integrating defense infrastructure between its members. The organization of Pillar II around modular projects rather than major ones offers opportunities to scale across regional allies. Japan and South Korea have already signaled interest in participation on a project-by-project basis. Their willingness to do so underscores how AUKUS can operate as more than a trilateral partnership, with implications for the region at large. As states in the region continue to seek new forms of security cooperation in order to deepen domestic defense capacities, Pillar II of AUKUS presents itself as a potential strategic framework and model for future security cooperation that can be extended throughout the Indo-Pacific.

Unlike traditional mutual defense treaties–such as those the U.S. currently maintains with Japan, South Korea, the Philippines, and Australia–membership in AUKUS does not obligate states to intervene on behalf of one another during conflict. Pillar II cooperation is therefore premised not on mutual defense commitments, although its constituent states currently do maintain such a commitment to one another, but on shared interests in preserving a favorable strategic environment. This model is particularly well-suited for ASEAN members, whose states seek to enhance their regional security without engaging in formal alignment. Thus, cooperation under Pillar II can be pursued selectively and in accordance with domestic political constraints. 

The key strategic advantage of Pillar II lies in its ability to lower the political cost of cooperation, while increasing the strategic value of deterrence. Enabling states to gain access to advanced technologies and intelligence sharing networks, without entering binding military alliances, would prove to be a major advantage to states existing in an environment defined by competitive influence and national autonomy. 

Implications for Southeast Asia

Recent developments in regional security, including the increased engagement with networked alliance structures such as AUKUS and the recently developed U.S.-South Korean nuclear submarine partnership, come at a time when Southeast Asian states are reassessing the foundations of their security relationships. ASEAN members have maintained a longstanding preference for non-alignment and avoiding entanglement in great power rivalry since their emergence as independent nations in the context of the Cold War. However, as tensions between the United States and China heighten, these nations have found it increasingly difficult to maintain the traditional posture of non-alignment, increasing demand for reliable security partnerships.

AUKUS itself is unlikely to expand into Southeast Asia, due to the variance in domestic industrial capacity between existing AUKUS members and countries in Southeast Asia, but the underlying structure and principles of Pillar II still offer a framework for the emergence of new networks of defense cooperation. Since Southeast Asian states have historically sought capacity without alignment, the organizational framework of Pillar II offers a pathway for engagement that fits the domestic political constraints and reality of a wide array of existing domestic industrial capacity. The U.S. has several Comprehensive Strategic Partnerships (CSPs) in the region that can serve as platforms for future defense cooperation. The elevation of U.S.-Vietnamese relations to a CSP in 2023 remains the most recent development in this respect, signalling Vietnam’s willingness to pursue deeper technology and defense cooperation with the U.S. in the wake of a powerful China. The U.S. also maintains CSPs with Indonesia, the Philippines, and a collective partnership with ASEAN as a whole, which provides an existing diplomatic basis through which targeted capacity-building can occur. The U.S. could therefore work to translate the diplomatic architecture of its existing CSPs into concrete, defense cooperation arrangements tailored to each state’s needs and political limits.  

As China continues its military buildup of conventional and nuclear forces, defense technology has become a priority for the U.S. in the region. In 2023 alone, the U.S. Department of Defense spent over $1.2 billion on “partner capacity-building efforts” in the region, which constitutes roughly one third of its entire international security cooperation budget. Ongoing U.S. efforts and defense partnerships in the region show a willingness to engage in cooperative domains to expand domestic capacities of states in the region, however these efforts often remain fragmented and limited in scope. Further efforts by the U.S. demonstrate its willingness to pursue these goals, such as through the Principles for Indo-Pacific Industrial Resilience (PIPIR), in which the U.S. seeks to expand opportunities for the joint production and sustaining of weapons with partner nations. Critical efforts such as these not only strengthen the position of the U.S. in the region amidst growing regional competition, but allows the joint research and development and industrial engagement necessary to bolster the domestic capacity of regional allies to resist external coercion. 

The Future of Southeast Asian Security Architecture

The ongoing shifts within the Southeast Asian Security Architecture suggest an opportunity for the U.S. to strengthen its position through more distributed and capability-based partnerships in Southeast Asia, rather than formal alliance blocs. In this new security environment, states can engage in defense cooperation not through a single overarching institution, but through overlapping arrangements based on the unique strategic needs and industrial capacity of each state. By building off of the hub-and-spoke strategy that the U.S. has developed throughout the Indo-Pacific, a similar cooperative framework hinged on technological integration and capability building can be implemented–rather than direct security commitments–preserving both the interests of Southeast Asian nations in maintaining domestic autonomy and offering a more credible mode of security commitment as the U.S.’s traditional mutual-defense obligations begin to falter in the region. 

The next phase of regional security cooperation is likely to take place in domains where offensive escalation risks are low, but the benefits of establishing a significant deterrence capability remain high. Cyber defense, secure communications, space-based intelligence, and data-sharing systems represent areas in which Southeast Asian states have clear vulnerabilities and strong incentives to cooperate. Strengthened capacity in these areas would reinforce sovereignty and improve states’ ability to manage potential crises, resist coercion, and defend against rising political pressure in the region. 

The development of these networks will however encounter various challenges. China may interpret the deepening of capability networks as evidence of containment, and respond with intensified economic pressure or escalatory gray-zone military activities in maritime spaces as in the past. Because of this, Southeast Asian governments and the U.S. must manage their cooperation cautiously so as not to provoke destabilizing reactions. Maintaining ASEAN cohesion should also be prioritized when forming these capability-building relationships. The complexity of Southeast Asia means the differing interpretations of national interest, strategic culture, and economic dependency of individual states could pose challenges to attempts at building shared security frameworks throughout the region that must be taken into account. Finally, the U.S. must ensure that its own defense-industrial capacity is sufficient to support multiple overlapping technology partnerships at scale. Without reliable delivery timelines and clear sustainment pathways, confidence in this capability-based cooperation framework could falter. 

This shift toward capability-based security networks further provides an alternative pathway for the U.S. and to make inroads within the regional order at a time when China continues to expand its regional influence through projects such as the Belt and Road Initiative (BRI). Although increased security cooperation akin to a Pillar II-based security agreement and the infrastructure focused vision of China’s BRI are distinct mechanisms, both are vital assets to achieving long-term strategic relationships in the region. Capability integration generates a different form of structural interdependence based on shared technological development, joint cyber defense frameworks, and information and intelligence sharing networks. These initiatives would reinforce American involvement in Southeast Asia, and direct new investment into the domestic and allied industries necessary for the development and upkeep of these networks. In this sense, capability-based cooperation offers Washington a means to reassert regional influence through sectors where it maintains a comparative advantage, even as China leverages its economic instruments to shape the preferences of regional states. This emerging security architecture is thus reflective of a broader strategic reality in which the regional order is shaped increasingly not only by economic interdependence, but by the diffusion of defensive capabilities that bind partners together through technological and operational interdependence. 

Work Cited

¹ Bryan Clark, Seth Cropsey, and Timothy Walton, Sustaining the Undersea Advantage: Disrupting Anti-Submarine Warfare Using Unmanned Systems (Washington, DC: Hudson Institute, 2020)

² Australian Government, Department of Defence, National Defence: Defence Strategic Review 2023 (Canberra: Commonwealth of Australia, 2023), https://www.defence.gov.au/about/reviews-inquiries/defence-strategic-review

³ “Lessons from the Ukraine Conflict for Modern Warfare: Age of Autonomy, Information, and Resilience,” Center for Strategic and International Studies, January 26, 2023, https://www.csis.org/analysis/lessons-ukraine-conflict-modern-warfare-age-autonomy-information-and-resilience

⁴ “Technology, Complexity, Uncertainty, and Deterrence,” Henry A. Kissinger Center for Global Affairs, Johns Hopkins SAIS, n.d., https://kissinger.sais.jhu.edu/programs-and-projects/kissinger-center-papers/technology-complexity-uncertainty-and-deterrence/

⁵ “The President’s News Conference With Prime Minister Fumio Kishida of Japan,” The American Presidency Project, April 10, 2024, https://www.presidency.ucsb.edu/documents/the-presidents-news-conference-with-prime-minister-fumio-kishida

⁶ “AUKUS Pillar II: Joint Statement by the Prime Minister of Australia, the Prime Minister of the United Kingdom and the President of the United States,” ParlInfo, Parliament of Australia, April 9, 2024, https://parlinfo.aph.gov.au/parlInfo/download/media/pressrel/9722641/upload_binary/9722641.pdf#search=%22media/pressrel/9722641%22

⁷ “Seoul’s Nuclear Submarine Breakthrough,” German Marshall Fund of the United States, May 2, 2024, https://www.gmfus.org/news/seouls-nuclear-submarine-breakthrough

⁸ “Southeast Asia’s Evolving Defence Partnerships,” Lowy Institute, December 12, 2023, https://www.lowyinstitute.org/publications/southeast-asia-s-evolving-defence-partnerships

⁹ “Making AUKUS Work: The Case for an Indo-Pacific Defense Innovation Consortium,” Atlantic Council, n.d., https://www.atlanticcouncil.org/in-depth-research-reports/issue-brief/making-aukus-work-the-case-for-an-indo-pacific-defense-innovation-consortium/

¹⁰ “Making AUKUS Work”

¹¹ “FACT SHEET: Partnership for Indo-Pacific Industrial Resilience (PIPIR),” U.S. Department of Defense, June 2, 2025, https://media.defense.gov/2025/Jun/02/2003730341/-1/-1/1/FACT-SHEET-PARTNERSHIP-FOR-INDO-PACIFIC-INDUSTRIAL-RESILIENCE.PDF

¹² “Assessing the Risks of Chinese Grey-Zone Activities,” RAND Corporation, 2024, https://www.rand.org/content/dam/rand/pubs/research_briefs/RBA500/RBA594-1/RAND_RBA594-1.pdf

¹³ Congressional Research Service, “U.S. Defense Industrial Base and Indo-Pacific Partnerships,” May 22, 2023, https://www.congress.gov/crs-product/R47589