Five days in August 2026 captured a quiet transformation in Southeast Asia’s security architecture.
On 21 August, Indonesia hosted China for their second foreign and defence ministers’ 2+2 dialogue, where the two sides agreed to strengthen military-to-military mechanisms, information exchange and cooperation on cyber and transnational security.
Five days later, Indonesian foreign and defence ministers met their Australian counterparts in Melbourne for their tenth 2+2, the first since the signing of the Jakarta Treaty on Common Security.
On the same day, the defence ministers of Indonesia, Australia and Japan held their inaugural virtual trilateral meeting.
None of these arrangements replaced ASEAN.
In fact, ASEAN defence officials met through the ADSOM and ADSOM-Plus on 26–27 August, almost as these bilateral and minilateral arrangements deepened.
The juxtaposition reveals an increasingly important distinction: ASEAN continues to provide the region’s diplomatic architecture, while some of the most operational forms of security cooperation are increasingly being delivered through smaller networks.
Southeast Asia is not moving beyond ASEAN so much as building around it.
The region is developing a layered security order in which ASEAN centrality increasingly depends not on being the exclusive venue for security cooperation, but on its ability to coordinate arrangements that it does not directly control.
ASEAN is still central, but no longer sufficient on its own
ASEAN’s institutional role should not be understated.
The ASEAN Regional Forum’s Manila Plan of Action for 2026–2036 still describes the ARF as a central pillar of the evolving regional security architecture.
The ASEAN Defence Ministers’ Meeting remains the region’s highest defence consultative mechanism, while the ADMM-Plus has developed practical cooperation in areas such as maritime security, humanitarian assistance, peacekeeping, cyber security and counter-terrorism.
These mechanisms matter because they create habits of dialogue across countries that may otherwise have little strategic trust.
They also provide political legitimacy for cooperation between Southeast Asian states and major powers that are increasingly suspicious of one another.
The fact that China, the United States, Japan, Australia and other external partners continue to participate in ASEAN-led processes demonstrates that ASEAN still offers something few smaller groupings can: an inclusive venue in which strategic competitors can communicate without first resolving their disputes.
But inclusiveness comes with limits.
Decisions are slower, political sensitivities are greater and practical cooperation often has to remain voluntary and non-binding.
Those features are not necessarily institutional failures. They are partly the cost of maintaining a forum that includes countries with very different threat perceptions and strategic preferences.
The problem is that many contemporary security challenges require forms of cooperation that large ASEAN-led mechanisms are not designed to provide quickly.
Intelligence sharing, logistics access, military interoperability, defence technology, cyber cooperation, joint planning and contingency coordination require higher levels of trust and political specificity.
These are precisely the areas where bilateral and minilateral arrangements have proliferated.
Operational security is becoming networked
The trend is visible across the region.
Japan and the Philippines have brought a Reciprocal Access Agreement into force, signed an Acquisition and Cross-Servicing Agreement and expanded operational cooperation through exercises such as Balikatan.
Australia and Japan are also deepening interoperability across military domains.
Indonesia provides an even more revealing case because it is not simply joining one strategic camp.
Jakarta is institutionalising security ties with several major powers at the same time.
With China, Indonesia has established a foreign and defence ministers’ 2+2 mechanism and a Comprehensive Strategic Dialogue.
The August 2026 meeting agreed to strengthen direct military-to-military mechanisms between the Indonesian Armed Forces and the People’s Liberation Army, alongside cooperation on cyber security, law enforcement and information exchange.
With Australia, Indonesia is moving to operationalise the Jakarta Treaty and the 2024 Defence Cooperation Agreement.
The tenth 2+2 in Melbourne discussed practical defence and security initiatives in what both sides described as a deteriorating geostrategic environment.
Indonesia’s ties with Japan have also deepened.
The two countries revived their 2+2 mechanism in November 2025 after a gap of more than four years, and their defence relationship has since expanded through ministerial exchanges, equipment cooperation and operational engagement.
The inaugural Japan-Australia-Indonesia defence ministers’ meeting in August 2026 adds a new trilateral layer to those bilateral ties. This pattern matters because it complicates the common argument that minilateralism inevitably undermines ASEAN.
In Indonesia’s case, the same government that repeatedly defends ASEAN centrality is actively constructing security relationships outside ASEAN-led institutions.
The contradiction is only apparent. Jakarta is using different institutions for different purposes. ASEAN offers diplomatic legitimacy, political inclusiveness and regional norm-setting.
Smaller arrangements offer speed, trust and operational delivery. Southeast Asian states increasingly need both.
The real risk is fragmentation, not replacement
The most important question, then, is not whether minilateralism will replace ASEAN. It is whether multiple layers of security cooperation can coexist without producing fragmentation.
Layered security arrangements can strengthen regional resilience. They allow countries to respond to specific security needs without requiring consensus across all ASEAN members.
They can also reduce overdependence on a single major power by giving Southeast Asian states multiple channels for defence cooperation.
But the same flexibility can create problems.
Different arrangements may develop incompatible operating standards, separate information-sharing practices and divergent strategic assumptions.
Some networks may become increasingly tied to the strategic preferences of external powers. Others may remain politically symbolic without developing real capability.
The danger is a region in which security cooperation becomes denser but less coherent.
This challenge is particularly acute because Southeast Asian states do not share identical threat perceptions:
The Philippines views its alliance with the United States and deepening defence cooperation with Japan through the lens of maritime pressure in the South China Sea.
Indonesia seeks to deepen security ties with China, Australia and Japan while preserving non-alignment.
Other ASEAN members may prefer more limited military engagement with external powers.
If these different networks continue to expand without mechanisms for transparency and coordination, ASEAN centrality could become rhetorical rather than functional.
The region would still meet under ASEAN auspices, but the most consequential security decisions could increasingly be taken elsewhere.
Centrality should mean orchestration
ASEAN therefore needs to reinterpret what centrality means.
Centrality should no longer depend on the assumption that all meaningful security cooperation must take place through ASEAN-led institutions.
That expectation is increasingly unrealistic.
Instead, ASEAN should aim to become the institution that connects, coordinates and disciplines the wider network of security arrangements emerging around it.
In practical terms, ASEAN could begin with greater transparency.
The ADMM and ADSOM should maintain a regular regional mapping of major bilateral and minilateral defence arrangements involving ASEAN members, including exercises, access agreements, logistics cooperation, information-sharing initiatives and new defence dialogues.
Such a mechanism would not give ASEAN authority over sovereign bilateral arrangements. Nor should it. But it would give member states a common picture of how the region’s increasingly dense network of defence relationships fits together.
ASEAN could also build stronger interfaces between minilateral activities and existing ASEAN mechanisms.
Exercises conducted by smaller groupings in humanitarian assistance, maritime security or disaster response could share lessons with relevant ADMM-Plus Experts’ Working Groups.
Crisis communication procedures developed in bilateral arrangements could, where technically and politically feasible, be made compatible with ASEAN’s Direct Communications Infrastructure, which is itself being further developed.
This need not turn ASEAN into a military alliance or a supranational security manager.
The objective is much more modest: to reduce the risk that numerous security arrangements involving ASEAN members evolve into separate institutional islands.
A third priority is therefore to protect ASEAN’s convening role.
ASEAN-led institutions should remain the place where overlapping security networks explain their activities, discuss potential frictions and develop common expectations for behaviour.
This function may sound less dramatic than joint military exercises, access agreements or defence procurement. But in an increasingly fragmented regional environment, the ability to make competing networks communicate with one another could become ASEAN’s most valuable security contribution.
The objective should not be to force every security initiative back under ASEAN control. It should be to prevent overlapping networks from becoming strategically disconnected from one another.
Indonesia can help redefine centrality
Indonesia has a particular role in this process.
Its simultaneous engagement with China, Australia and Japan gives Jakarta experience operating across security networks that do not share the same strategic orientation.
This differs from simply joining a US-centred alliance network or building a counter-China coalition.
Indonesia’s approach reflects a broader preference for maintaining strategic room for manoeuvre. Yet that preference now requires institutional management.
The greater the number of security relationships Jakarta develops, the greater the need to ensure that individual arrangements do not inadvertently pull Indonesia or the wider region toward incompatible strategic commitments.
This gives Indonesia an opportunity to translate its own experience into a regional agenda.
Jakarta could advocate greater transparency between ASEAN-led and minilateral activities, stronger crisis-communication linkages and basic principles of institutional compatibility.
It could also encourage states in smaller arrangements to brief relevant ASEAN forums on initiatives with wider regional implications.
Such proposals would allow Indonesia to defend ASEAN centrality without pretending that ASEAN must conduct every significant piece of regional security cooperation itself.
That distinction matters.
A central institution does not have to be an exclusive institution.
From exclusivity to orchestration
For decades, debates about ASEAN centrality have often asked whether ASEAN remains “in the driver’s seat”. That metaphor is becoming less useful.
Southeast Asia’s emerging security architecture looks less like a single vehicle and more like a network of intersecting routes.
ASEAN does not need to drive every one of them. But it does need to ensure that they do not collide.
Developments in August 2026 show that this transition is already underway. ASEAN-led meetings continue, but bilateral 2+2 dialogues, trilateral defence consultations, access agreements and operational partnerships are becoming equally important features of the regional security landscape.
This does not necessarily weaken ASEAN. It changes the job ASEAN has to perform.
ASEAN centrality is shifting from exclusivity to orchestration.
If ASEAN can no longer monopolise regional security cooperation, its relevance will depend on its ability to coordinate it.
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Probo Darono Yakti is a Lecturer in International Relations and Secretary of the Department of International Relations at Universitas Airlangga, Indonesia. He is also Deputy Executive Director of the Center for National Defence and Strategic Studies (CNDSS). His research focuses on Indonesian foreign policy, strategic studies, maritime security, geo-economics, and the evolving Indo-Pacific security architecture.
(QOB)