Modernizing Indo-Pacific Partnerships: From the Japan-ROK Bilateral to the JAROK (Japan-Australia-ROK) Pillar

Prof. Iwama Yoko | Professor, National Graduate Institute for Policy Studies (GRIPS)

Download Article PDF

Introduction

For several years, U.S. alliances both within the Indo-Pacific and between Europe and the Indo-Pacific blossomed. The trend started with the rise of China in the 2000s and accelerated with the Russian invasion of Crimea in 2014. The first NATO-IP4 (Indo-Pacific Four: Japan, Korea, Australia, New Zealand) meeting was held in 2022 in Madrid, and the format became an established forum. The Biden administration further solidified multilateralism in East Asia by forging a Japan-Korea-U.S. cooperation mechanism at the Camp David summit in August 2023.

However, from the outset of the Trump 2.0 administration, there has been a resetting of American priorities. European alliances have been hardest hit. Since 2025, NATO seems to have been continuously in crisis. Europeans are spending much more on defense and are now mainly shouldering the burden of military support for Ukraine. They have also initiated new consultations about nuclear and conventional deterrence in Europe.^[1]

When it comes to America’s Asian alliances, three points can be made:

(1) The United States is asking regional allies to shoulder more of the burden;

(2) The Trump administration is more bilateral than multilateral in its approach; and

(3) The Trump administration defines American national interest in economic rather than military terms.

America’s 2025 National Security Strategy states that “the Indo-Pacific is already and will continue to be among the next century’s key economic and geopolitical battlegrounds.” This economic-centric view of the world is characteristic of the Trump administration. The U.S. national interest is defined more in economic terms, and security is viewed as secondary to the economic advantages that the region or issue will bring. The recent visit to Beijing by President Trump showed how much economic advantage counts even in strategic matters like Taiwan. Europe is already debating how to reimagine NATO and replace American extended deterrence.^[2]Asia must also think about Plan B.

Although President Trump has never spoken of leaving Asia, the administration is clearly requiring the region’s partners to do more. At the 2025 Shangri-La Dialogue, Secretary Hegseth said that “it doesn’t make sense for countries in Europe to do that while key allies in Asia spend less on defense in the face of an even more formidable threat.” The 2025 National Security Strategy speaks about “Burden-Sharing and Burden-Shifting,” but the situation has become even more acute since then. America is bogged down in a protracted war in the Middle East and is so depleted of weapons that it cannot provide Japan with the Tomahawk missiles it promised.

The Indo-Pacific does not have a NATO, and for many reasons, it is not practical to think about one. But we must strengthen the regional pillar in the Indo-Pacific. We should do this first by strengthening the bilateral Japan-Korea relationship. Since the Trump administration has not shown as much interest as the previous government in strengthening multilateral cooperation, the Japan-U.S.-Korea trilateral is likely to remain stagnant. But we can strengthen the weakest link of the trilateral, the Japan-Korea link, in order to revive multilateralism when the time is ripe. We should also bind this Japan-Korea link with Australia, so that we have a strong Japan-Australia-ROK (JAROK) pillar in the Indo-Pacific. The Trump administration is right to consider the Indo-Pacific as central to world affairs, and Asian nations should stop thinking in Eurocentric terms for alliances. Japan and Korea no longer belong to the “Far East,” which is a term originating from Europe. In reality, Europe has become the “Far West,” and Asia is central to the world balance of power in the 21^stcentury.

Strengthening Japan-ROK Relationship

How can we strengthen Japan-Korea ties? The 2025 NSS asks Japan and Korea to “increase defense spending, with a focus on the capabilities—including new capabilities—necessary to deter adversaries and protect the First Island Chain.” Much has already been discussed between the Prime Minister of Japan and the President of the ROK in their August 2025 and January 2026 meetings. In spite of worries from both sides, the two summits proceeded in a candid and cordial atmosphere. Following on from this, there are three things that need to be done.

(1)   Institutional framework for strengthening political cooperation

The two countries have been working in recent years to strengthen bilateral ties. The shuttle diplomacy between the leaders has become regular, and it has been reported that the two countries have agreed to set up a 2+2 (Defense and Foreign Ministries) dialogue on the vice-ministerial level. I have argued in the past for “Élysée Treaty”-type institutionalization of the ROK-Japan bilateral relationship, and this is needed now more than ever. Between France and Germany, the foreign and the defense ministers are obligated to meet at least once every three months, and high-level talks of the foreign ministries need to take place every month. The chiefs of staff also need to come together once every two months. It has been more than 60 years since the normalization of the Japan-ROK relationship. Considering the importance of this relationship, the countries need a basic treaty to solidify the bond. Such a treaty should also encompass social and educational aspects, including the exchange of youths.^[3]

(2)   Alignment of defense-industrial production capabilities

This is important in terms of both security and economics. The ROK now has robust production capabilities in many industries, including semiconductors, EV batteries, steel, and shipbuilding, which are key to a resilient crisis economy and supply chain. It also has a flourishing defense industry, with exports reaching $15.4 billion in 2025. Poland is now the main purchaser, with huge contracts for K2 main battle tanks, K9 howitzers, K239 rocket launchers, FA-50 light fighters, and more. Japan has liberalized its defense exports, abolishing the so-called “five criteria” for the export of arms this year. The sale of the Mogami-class frigate made headlines in August 2025, and the Takaichi government is moving to push more defense industry development with public funding.

Japan and the ROK will benefit from clever coordination. What is remarkable about Korean weapons exports is the speed of delivery and companies’ willingness for technology transfer and local production. Being so close to each other geographically, Korea and Japan will need to assist each other in times of crisis. The two governments should sign the Acquisition and Cross-Servicing Agreement (ACSA) as quickly as possible, but they need to go further. With wars being fought simultaneously in Ukraine and the Middle East, we are already in a crisis economy mode. Japan and Korea need a framework to coordinate their economies so they can best assist each other and other allies, including the United States, in times of crisis. If the two countries can also come up with a common investment plan to reinvigorate production in the United States in certain sectors, that would be even more beneficial.

(3)   Japan-ROK deterrence and non-proliferation dialogues

With the United States redefining relationships with its allies, there is considerable risk that the credibility of U.S. extended deterrence will weaken and unprecedented nuclear proliferation will occur. Many Japanese suspect that the ROK is on its way to acquiring nuclear weapons, and the ROK’s decision to construct nuclear-powered submarine (SSN) is the first step on that route. The Japanese security establishment is also considering the acquisition of a nuclear-powered submarine, and this project will likely be mentioned in the upcoming three national security documents due by the end of 2026. Despite the recent friendly tone, there is still ample rivalry between Japan and the ROK, and these suspicions could feed into an arms race.

Both Japan and the ROK rely on the credibility of U.S. extended deterrence. It is in the interest of both countries that they work together to strengthen this credibility and maintain the NPT regime, including the denuclearization of North Korea. In order to avoid unnecessary misunderstandings of each other’s intentions, Japan and the ROK need to communicate with each other on these issues. France and the United States have initiated such a dialogue after President Macron’s Ille-Longue speech on nuclear deterrence.^[4]This included participants from both sides’ foreign affairs, defense and energy agencies. They have decided to establish an annual bilateral dialogue and a working group. Japan-ROK also needs such a dialogue, which deals with both military and energy-related nuclear issues.

Further consideration should be given as to whether this strategic stability dialogue may at times be held with the United Kingdom and France. These two are nuclear weapon states but have far fewer nuclear weapons than the United States. Their deterrent forces are meant to be complementary to those of the United States. As the United States’ position changes, they may feel the need to adjust their policies. Both have announced policies to strengthen their nuclear arsenals but have not changed their fundamental thinking about deterrence. Countries like the ROK and Japan need to have a full understanding of the changes taking place, since this is a matter that affects global stability. They also need to understand that relatively smaller nuclear arsenals are only complementary to and not a substitute for the deterrence provided by the United States.

Building JAROK (Japan-Australia-ROK) Pillar in Indo-Pacific

We need to be aware that the Indo-Pacific will be the center, not the periphery, of global events in the coming decades. This will be the theater where strategies of giants collide. The 2025 U.S. National Security Strategy admits that strengthening alliances here will make the Indo-Pacific “the bedrock of security and prosperity long into the future.” So it shall be, but the regional allies need to rethink their role. Rather than following what the United States dictates, Asian countries must shape the environment themselves. We need to create a regional pillar connecting Japan, Australia, and the ROK. Let us call it the “JAROK Pillar” of the Indo-Pacific. These three countries are the most stable and prosperous democracies in the region. They should hence try to consolidate this JAROK pillar as the foundation of the stability and prosperity of the region. Work in the Japan-Australia-ROK trilateral format started in June 2024 with an inaugural official-level Indo-Pacific dialogue between the countries. This was followed by a Track 1.5 dialogue hosted by the U.S. Studies Center of the University of Sydney.^[5]

There are currently many minilaterals in the Indo-Pacific, including U.S.-Japan-Australia; U.S.-Japan-ROK-Philippines-New Zealand, and so on. Recently, the Balikatan exercise was conducted in the Philippines with several partners present, including Japan, Australia, the United States, and the ROK. There are also strong bilateral relations between Japan and Australia and between the ROK and Australia. But we need an institutional framework to promote military coordination in the absence of the United States. That is not to say the United States will retreat from Asia, but there may be situations in the early stages of a crisis where the United States is unable to be physically present from day one, and the local powers must take the lead. The United States will still be providing vital assistance, but we must be capable of planning and operating even without the Americans being present. Currently, we do not have the institutional capacity to plan and operate in the absence of America. But we must think about such scenarios.

This is not to say that we will create a new alliance, nor are we trying to create an Asian NATO. Such a rigid structure will not suit the Indo-Pacific’s varied members and geography. We must retain flexibility so that members and actions can be coordinated according to the needs of the scenario. But we need a control tower in order to coordinate the regional powers if the United States is engaged elsewhere. Japan, Australia, and the Republic of Korea are technologically and militarily advanced middle powers in the region with a willingness to collaborate and should take on this role. Other smaller powers and regional actors will collaborate according to their needs, case by case, but JAROK needs to be able to consult with each other immediately and come up with responses in an Indo-Pacific crisis. If the United States is there, so much the better, but we also need to be prepared to act regionally.

We also need a local supply chain of critical weapons and ammunition in case of crisis. Relying solely on the United States is not a solution, as ongoing conflicts have shown. We must consolidate the resources and the production capability of the region and design a robust logistics network. This will probably involve other regional players, but JAROK should be willing to lead.

Another way of strengthening the interaction between the three countries would be to associate Japan and the ROK with AUKUS and then create a minilateral within this framework. It is possible that we have three countries aspiring to operate nuclear-propelled submarines in this region in the coming decades. Currently, these three are pursuing their possibilities separately. It would at least be in the interest of regional stability that they exchange information about their intentions and progress. If they go ahead with the acquisition of nuclear-propelled submarines, they will all need to redefine their relationship with the IAEA in terms of the NPT regime.

Of the three countries, only Japan has enrichment and reprocessing capabilities. The U.S. Department of Energy announced in January 2026 its intention to invest $2.7 billion to strengthen domestic uranium enrichment services over the next ten years. But details are still unknown, and whether and in what forms the ROK will receive the fuel for its nuclear-propulsion submarine remains unclear. Nuclear energy technology is entering an inflection point where new technologies are being developed quickly. Depending on what kind of power plant technology becomes dominant in the future, different kinds of enriched uranium fuel will be needed. The three should coordinate amongst themselves rather than wait for U.S. leadership, since the United States will likely not play a dominant role in multilateral forums.

Japan and ROK participation will benefit AUKUS in many other ways as well. When it comes to Pillar II, Japan and the ROK together possess advanced capabilities, such as undersea sensing, anti-submarine warfare, semiconductors, shipbuilding, cyber capabilities, and ammunition production. Should Japan and Korea join AUKUS for these reasons, it would add up to “JAUKKUS (Japan-Australia-UK-Korea-US).”

But since the United States will likely not take the lead in multilateral settings in the next several years, we can create minilateral groupings within JAUKKUS in the meantime. A JAUKROK (Japan-Australia-UK-ROK) format would be useful in many cases, since all participants will benefit from the UK’s knowledge of nuclear submarines.

We could have willing partners in the region associate themselves with this pillar as necessary. New Zealand and the Philippines are probable partners in many situations, since they share many values and security concerns with other countries. The two may choose to become full members when the time is ripe. Other ASEAN partners will also be able to join in issue-oriented ways and conduct regular exercises. For these reasons, the United States will benefit from an active JAROK pillar that helps prepare an environment on which U.S. armed forces can count.

Toward an Indo-Pacific Union

The Trump administration is right in considering that economic viability is the decisive factor in alliances. The JAROK pillar needs to work to integrate other younger economies of the region to facilitate growth and stability. Here again, JAROK can lead, since the three have similar economic and social standards based on the rule of law, which provide the predictability and accountability essential for stable and reliable growth. Starting with major ASEAN countries, we should aim for more economic and social cooperation in the region. The CPTPP is an important framework, but we should strive for a region where not only goods but also people move much more freely. JAROK countries will benefit from the younger populations of ASEAN countries studying and working in their aging economies.

However, this needs to be done in a rules-based and orderly way that does not endanger the safety and security standards that JAROK countries have already achieved. In order to do this, work should be done to reform regulatory and administrative standards in ASEAN and other partner countries, while at the same time reducing over-regulation in JAROK countries. The European Union provides a model in some ways, but the future “Indo-Pacific Union” should aim for less supranational integration. Although we do share some kind of Asian identity, the region is much more diverse in many ways, so our union need not be bound as closely together as the EU.

Conclusion

Creativity is required in times of crisis. America may no longer be the country we used to know, but neither are we. The world keeps changing, and we need to keep reforming and modernizing. America will still remain committed to the Indo-Pacific, but it expects us to take the lead. The United States is still the largest economy in the world, but its share in the world GDP is now around 25%, compared to 40% in the 1960s. We should no longer be bound by past habits and instead start thinking outside the box. In the past, we were used to having an American “hub” that connects us all and gives us direction. That needs to change. We need to become the hub to which America will give assistance. So, this is why we need a strong Japan-Australia-ROK (JAROK) pillar in the region, to which other Asian nations can integrate socially, economically, and politically.

Notes

---

^[1] Kiel Institute for World Economy has been tracking aid to Ukraine. It is very clear that Trump administrations aid for Ukraine has decreased dramatically. https://www.kielinstitut.de/publications/news/ukraine-support-after-4-years-of-war-europe-steps-up/

^[2] European security specialists have started contemplating how to replace U.S. nuclear deterrence. See Report by European Nuclear Study Group “Mind the Deterrence Gap: Assessing Europe’s Nuclear Options,” (Feb 2026) DOI: 10.47342/SNSE5421. On discussions to replace NATO, see “Europe’s secret Plan B to replace NATO: what if America quits,” The Economist, May 19th 2026, https://www.economist.com/europe/2026/05/19/europes-secret-plan-b-to-replace-nato?giftId=ZTBjYjcyY2UtYTE2Yi00N2M2LThmMGUtNjE5OWUxODNmYTFm&utm_campaign=gifted_article

^[3] Yoko IWAMA, “Time for a Japan-Korea Élysée Treaty: The two East Asian nations should Take inspiration from landmark treaty in Europe,” The Diplomat, August 17, 2023. https://thediplomat.com/2023/08/time-for-a-japan-korea-elysee-treaty/The original  Élysée Treaty(Treaty of Friendship between Germany and France) was signed on 22 January 1963. It has now been succeeded by Aachen Treaty on 22 January 2019.

^[4] Joint Statement on the U.S.-France Deterrence, Strategic Stability, and Non-Proliferation Dialogue, the U.S. Department of State, Office of the Spokesperson, March 11, 2026.https://www.state.gov/releases/office-of-the-spokesperson/2026/03/joint-statement-on-the-u-s-france-deterrence-strategic-stability-and-non-proliferation-dialogue

^[5] Thomas Wilkins, ‘“Middle Power Minilateralism”: The Australia-Japan-Korea Trilateral Diplomacy,’ JFIR Commentary, No. 158, January 24, 2025. https://www.jfir.or.jp/en/commentary/4547/#_edn8; Christopher Watterson, ‘Seizing the moment: Outcomes of the inaugural Australia-Japan-South Korea trilateral dialogue’, (18 Sept 2024). https://www.ussc.edu.au/outcomes-of-the-inaugural-australia-japan-south-korea-trilateral-dialogue

About the Author

Prof. Iwama Yoko

Professor, National Graduate Institute for Policy Studies (GRIPS)

Prof. IWAMA Yoko is a professor at the National Graduate Institute for Policy Studies (GRIPS) and the director of Security and Strategy Programme at GRIPS. Having served as a research assistant at Kyoto University (1994-97), special assistant of the Japanese Embassy in Germany (1998-2000), and associate professor at GRIPS (2000), she was appointed professor at GRIPS in 2009. Her specialty is international security and European diplomatic history, focusing on NATO, Germany, and nuclear strategy.