by Wilson Tang
This article was written by a graduate student at the University of Hawai‘i at Mānoa as part of their research with the Indo-Pacific Policy Lab.
Abstract
Formal alliances between sovereign states, especially their militaries, are often difficult to assemble due to changing national interests or long-standing policy. Yet alliances, particularly US led ones as described in this white paper, are helpful to provide deterrence, both from military adversaries and to provide a robust defense on aspects of national infrastructure affected by non-traditional security concerns. However, formal alliances, though strong, involve binding legal obligations that may put off prospective member states. Informal or flexible alliances networks arose as a need for states to work together and to provide what the US describes as integrated deterrence, without binding legal obligations or other questions of sovereignty. But, interest must be continuously maintained.
Introduction
States have long recognized the benefits of working with another state to help reach national or strategic objectives. It may be a bilateral relationship or a formal intergovernmental organization, like the United Nations, the Association of Southeast Asian Nations (ASEAN), the North Atlantic Treaty Organization (NATO), African Union (AU), and the European Union (EU). These organizations help reduce the pressures of traditional security issues amongst states, but recently, non-traditional security (NTS) threats have become more prominent. Traditional security threats are the standard military threats, but non-traditional security threats consist of anything that could harm a country and its populace’s well-being. It can include, but is not limited to, migration, terrorism, food insecurity, piracy, natural disasters, climate change, supply chain disruption, economic well-being, and cybersecurity threats. These issues are not singular to one state; they are a multinational issues, affecting different states and crossing borders. Thus, its responses must be multinational in nature. Several formal regional intergovernmental organizations, such as the AU, ASEAN, and the EU, had taken the lead in responding to these issues. However, these formal organizations might require consent from all member states to tackle problems and thus might be slow to act or react to rapid changes. Formal alliances legally bind nation-states into agreements that impose responsibilities on member states when specific clauses are activated or compel modifications of national laws. While powerful, sovereign states have shown reluctance to enter formal alliances in recent times. Such inefficiencies and reluctance to enter more binding treaties lead to the rise of informal alliance minilateralism, a smaller grouping of states focused on specific policy goals. Within the United States, the government has begun to recognize that threats to the national and the citizens’ well-being are not limited to military threats, but also occur from natural disasters and supply-chain disruptions, as the 2020-2023 COVID-19 pandemic has proved. It recognized that its adversaries, such as the People’s Republic of China (PRC), Russia, and North Korea, are not only a military threat but also engage in “grey-zone” operations, including “lawfare”: the use of law to influence, damage or deter rivals; surgical use of military pressure; and cyberwarfare tactics to fulfill national objectives.
To counter both NTS and grey-zone operations and provide credible military deterrence, the US has turned to a concept called integrated deterrence. Integrated deterrence is the focused application of all government agencies, diplomatic support/signaling, political and economic pressure, and all aspects of military force, including cyberspace operations, operating in concert with supporting allies to provide a credible military deterrence. Integrated deterrence also advocates for the resiliency of state-critical infrastructures, expanding the concept of deterrence to the NTS field, especially in the realms of economic security.
This integrated deterrence concept has proved popular among the US and some of its allies, forming flexible alliance networks to create more responsive organizations. Thus, flexible alliance networks, such as the Quad, the I2U2 Group, and the American–Japanese–Korean trilateral pact, proved easy to establish and workable. This essay will discuss these informal alliance groups and their contributions to overall integrated deterrence. It will give an introduction on deterrence, the rise of informal flexible alliances, and discuss how these alliances allow governments to contribute to integrated deterrence by providing a forum for pooling resources, military forces, and to demonstrate a cohesive political will against would-be adversaries.
As flexible alliances are easier to create and sustain, they draw in countries with intermediate interests, and they are more applicable in Asian states, which are often reluctant to be part of major alliances. Flexible alliances help American and allies’ integrated deterrence by coordinating government abilities/movements and political will on specific topics. Still, these types of alliances may lack hard commitments and the resources provided by formal alliances, thus informal alliances operate in complement to or even as an extension of the formal alliance systems, such as going outside the stated bounds/goals of the alliance.
Deterrence Theory
The United States and its allies enter into these informal alliances for the purpose of deterrence. Deterrence is the action of discouraging another entity from attempting certain actions. In the international arena of states, deterrence is about discouraging another state from war or other hostile actions. It is the primary reason for the existence of an armed force. During the Cold War, the Soviet Union and the United States engaged in certain actions as a form of deterrence to each other. Both nations built military alliances, the Warsaw Pact and NATO, respectively, to deter conventional military aggression. They adopted a series of dead-hand or second-strike nuclear retaliation systems to adhere to the doctrine of mutually assured destruction, ensuring the rival’s launch of a first-strike nuclear attack would be self-destructive. These are examples of military and nuclear deterrence.
Michael J. Mazaar writes that there are two types of deterrence: the first is deterrence by denial. It aims to deter an adversary from an action by making “it infeasible or unlikely to succeed,” thus lowering the adversary’s confidence in attempting that action.[1] Examples of that type of deterrence might be having a larger naval force than another to deter naval invasions. The second type of deterrence is deterrence by punishment, it seeks to deter by threatening “severe penalties, such as nuclear escalation or severe economic sanctions, if an attack occurs.”[2] It strives to raise the cost of an action by attempting to offset the gains of that action. Mazaar continues by stating that deterrence by denial is “more reliable,” as it involves a display of hard military power, especially if one state’s military capability is plainly obvious to see.[3]
There are also two applications of deterrence, direct and extended. Direct is deterring an attack on one’s sovereign territory. Extended deterrence is about deterring adversaries from attacking allies. Mazaar writes that extended deterrence is the most difficult to do, as it requires the deterring nation to be willing to send military force to defend a location not at home.[4] Mazaar highlights the United States’ position and reluctance to fight for Europe, as demonstrated by the linchpin of NATO: Article 5 of the North Atlantic Treaty, in which member states accept the principle that an armed attack against one is an armed attack against all, but it does not trigger an automatic war-footing response, instead allowing each member state to decide on the escalation response.[5]
However, while military deterrence has a role, it has its limits. In an increasingly digital world, a straight military confrontation is not the only option as the threat environment has substantially evolved in complexity. It now operates in a multidimensional environment, with challenges from other nations. Military methods are not the only form of statecraft; now, a combination of political and economic pressure is used to weaken a state’s defenses. It is simply difficult to list all the attacks that can occur, but such attacks might involve a disinformation/misinformation campaign, cyberspace warfare, or even sponsorship of terror attacks. In response to this new competitive environment, the US and its allies turned to integrated deterrence.
Integrated Deterrence
The 2022 American National Defense Strategy (NDS) defined integrated deterrence as “the seamless combination of capabilities designed to convince all potential adversaries that the cost of any hostile activities will significantly outweigh their benefits.”[6] The NDS also defined the People’s Republic of China as its most likely “strategic competitor for the coming decades.”[7] It will also use all power, from economic resources, research and development, to strengthening the US military’s technological edge, to deter the PRC and other competitors. The 2022 NDS has written that it must first understand how competitors understand American interest, ally interest, combat credibility, the ability of the competitor to control escalation risks, and the evolution of the status quo.[8] The US Department of Defense (DoD) will develop innovative operational concepts, strengthen existing capabilities, and invest in mature, high-value assets, such as submarines, aircraft, supercarriers, and warplanes. The DoD will also invest in the research and development of new capabilities, such as hypersonic weaponry and “non-kinetic” systems, and bolster the resiliency of multi-domain attacks, which not only includes land, air, and sea attacks, but also those in the space and cyberspace domains as well. By hardening critical infrastructure, such as the energy grid, the weapons industry, and the internet cloud system, and by investing in military high-value assets, America aims to deter and maximize pain if conflict comes to pass. In short, America plans to “prioritise action in the face of a broad front of competitive interfaces.”[9] By working with allies, in concert with their strengths and limitations, America and its allies can reasonably provide a robust defense of their national and strategic interests. While American integrated deterrence is mainly geared towards military defense, such as the Quad and the American-Japan-South Korea Trilateral Alliance, the I2U2 Group will focus on NTS issues instead. Yet, all these informal alliances do tighten US commitment in the areas, providing a level of deterrence for member states.
The Rise of Flexible Alliances
Formal alliances, especially military alliances, are powerful, especially when they involve the principle of collective defense, which imposes a binding legal requirement that member states can assume a war posture if another member state has been attacked. It may also involve the creation of a single military command, such as the South Korea (ROK)/US Combined Forces Command, which allows a more streamlined and robust ability to act in an emergency instead of waiting for orders from a higher command. As part of containing communism in Asia, since the end of the Second World War, the United States and allies have formed many bilateral military alliances with some Asian states, such as Japan, South Korea, Thailand, the Philippines, and in the Oceania region, with Australia and New Zealand. In contemporary times, however, a single combined military command able to control troops of another nation may lead to questions, leading to issues of sovereignty. It may be difficult for a government to sell to its own citizens in a democratic country. In NATO’s example, every member state must also accept the prospective member state through their own democratic and legislative processes in ratifying foreign treaties. This ratification process may derail the accession process, as it did for Sweden, which had a harder time due to political issues from other member states, and only ascended to membership in 2024, compared to Finland in 2023, despite both applying for membership at the same time in a time of tensions with Russia. Joining a military alliance might provoke a hostile or actual armed response from the state the military alliance is perceived to oppose. Russia has been particularly hostile to the expansion of NATO, leading some European states to forgo NATO membership if it might invite a hostile confrontation. Arguably, it may have invaded Ukraine in 2022 over the question of NATO expansion to Ukraine. In Asia, the PRC is particularly uncomfortable with South Korea’s military alliance with the US, believing it to be “anti-Chinese” as well, and engages in economic coercion with South Korea if something occurs that the Chinese view as threatening to their interests. An example is the 2016 deployment of an American Terminal High Altitude Area Defense (THAAD) anti-ballistic missile system to South Korea, that could be seen as being used against China, despite “officially” being deployed against North Korea. These examples show that forming formal military alliances can be counterproductive. Yet their military deterrence value cannot be understated.
With overt military options often discouraged as a matter of statecraft, “gray zone conflict” has now become more popular. The US Special Operations Command defines gray zone conflict as “competitive interactions among and within state and non-state actors that fall between the traditional war and peace duality.”[10] Unattributed computer hacking, use of unmanned drones, sabotage of key economic infrastructure, such as gas pipes and undersea cables, disinformation and influence campaigns, GPS spoofing, and jamming are some of the measures of gray zone conflicts that states may face. Avoiding armed escalation while applying pressure in support of their objectives is a hallmark of gray zone conflicts. In the disputed zones of the South China Sea, China would build structures to assert and enforce its claims with the China Coast Guard and the Chinese Maritime Militia, shadowing and harassing non-Chinese ships out of the area. By using civilian vessels crewed by “patriots,” and vessels operated by Chinese law enforcement, China can avoid its actions being viewed as actions of war, and its more numerous and larger ships can outclass rival coast guard ships. The use of naval warships is generally avoided on both sides due to the risk of escalation. Other than gray zone conflicts, “hybrid warfare” has also emerged, combining conventional forces with gray-zone measures. Oftentimes, states have a difficult time responding to these actions, since they either have no legal or doctrinal response or lack assets or equipment, and military alliance treaties are unable to be used as these actions, though containing hostile intent, are not declared as “war.” Hence, flexible alliance networks rose to address these issues.
Flexible alliance networks may allow member states to have more autonomy, may be specific in one or some instances or topics, and may be formed or dissolved as situations dictate. In short, they allow states greater flexibility in addressing issues of concern or national security without the need to resort to formal alliances.
Case Study 1: Quadrilateral Security Dialogue
The liberal rules-based order is founded on international law as its basis of peace, with intergovernmental organizations to help promote peace, free trade, and human rights. Despite the world being seen as an anarchic environment, treaties and customary international laws, particularly of war and diplomacy, were generally accepted by many sovereign states. Justice has put international law into something that sovereign states have an obligation to adhere to. For example, despite the “gray-zone” measure from China, which is challenging the responses of the directly affected states, it was also very difficult to unite the states to counter it. One of these affected states, India, is not interested in defense blocs due to its non-alignment policy.
However, then Prime Minister Shinzo Abe of Japan started in a different direction, security is now not just physical security, but also from trade issues, hunger, and natural disasters. In a term called “securitizing,” matters of internal political importance, like hunger and poverty, were turned into matters of national security. In 2004, a particularly destructive earthquake and tsunami in the Indian Ocean affected at least 14 sovereign states directly. To coordinate a response to this disaster, the United States, Japan, India, and Australia formed the “Tsunami Core Group.”[11] This “Core Group” was the beginning of the Quad when Abe “added an ideological component” to the Core Group, proposing the creation of an “Arc of Freedom and Prosperity” to promote economic ties and safeguard the rules-based order, and unite like-minded states in 2006.[12] The United States signaled its interest, and then Australia, and then India. The leaders gathered in the ASEAN Regional Forum in Manila and even participated in a naval exercise, the Malabar. However, this incarnation of the Quad failed because China saw it as an anti-Chinese formation. Australia, in particular, was more vulnerable as its largest trading partner was China. In 2008, Prime Minister Kevin Rudd pulled out of the agreement. South Korea, while not part of the Quad, signaled its concerns that it might force Seoul to choose between China and the US, its respective closest trading partner and its closest security partner.[13] The Quad also lost momentum when Abe resigned the premiership due to ongoing health problems. The Quad was then suspended until 2017, when events began that caused the Quad to reform again. By 2017, China, under General Secretary Xi Jinping, had become more assertive in pursuing China’s national interests. China’s military forces have seen investments, particularly the Chinese Navy’s commissioning of the aircraft carriers Liaoning and Shandong, and the China Coast Guard has received several patrol cutters, including the cutter Nansha, noted for its large size in comparison with other patrol cutters in operation with other nations’ coast guards.
China increased its grey zone operations in the East and South China Seas and initiated a new foreign investment and infrastructure development plan known as the Belt and Road Initiative (BRI).[14] Through the BRI, it offered loans, grants, plus technical capabilities through Chinese companies to other countries. Unlike Western foreign aid, it is not tied to human rights development, hence allowing a larger part of acceptances, especially to African and Asian nations. Other problems include accusations of debt-trap diplomacy, making unsustainable loans to national state governments, and to projects with a questionable return on investments. An analysis by the Lowy Institute has written that smaller Pacific nations, due to their smaller economies, like Tonga, Samoa, and Vanuatu, are particularly vulnerable to Chinese debt.[15] China’s geopolitical influence has increased due to BRI, and created unease amongst the Quad members, suspicious of Chinese intent.
India, already having a long timeline of border disputes with China, is suspicious of China’s close relations with Pakistan, probably India’s greatest rival. India also had a military standoff with China in 2017 at the Indo-Chinese border at Doklam/Donglang, and China is blocking India’s entry into the Nuclear Suppliers Group (NSG), a multilateral group dedicated to “non-proliferation of nuclear weapons.”[16] Being an NSG member would allow easier access to nuclear materials. For the US, after a long period of concentration in the Middle East since 2003, it began to “pivot to Asia” under then-President Barack Obama, shoring up its existing relations there, especially as China began to exert itself. The election of Donald Trump as US President in 2016, and his more negative views of China has also brought more impetus for the Quad’s reformation. In Japan, Shinzo Abe had returned to the Premiership in 2012, and along with it tensions escalated with China over the Senkaku/Diaoyu Islands. China had repeatedly challenged Japanese control of the Islands with repeated incursions with air and seaborne assets around the Islands. Australia has become interested again after a change in government, and in its 2016 Defense White Paper, listed North Korean actions and the tensions in the East and South China seas as “creating uncertainty and tension” near the region of Australia.[17] The White Paper also stated its strategic defense interest to be in alignment with a “rules-based global order,” hinting at its unease of China’s growing military strength and their actions.[18]
With these concerns in mind, the US under Trump and Japan under Abe held a summit meeting, declaring a new Free and Open Indo-Pacific (FOIP) strategy, and created an integrated deterrence strategy with the government bodies in Japan and the US ordered to “flesh out detailed cooperation” in the rule of law, freedom of navigation, pursuit of economic prosperity and commitment for peace and stability.[19] In the face of Chinese and North Korean aggression, the second iteration of the Quad was restarted in the ASEAN Summit at Manila.
The new Quad functioned as an informal collective security forum, coordinating its members to bend all government and diplomatic ability to support a Free and Open Indo-Pacific. Since its re-founding, in 2020, the Quad members worked on COVID-19 mitigation measures. They had once again participated in the 2020 Malabar naval exercise. It even saw an expansion as the Quad “Plus,” seeing the inclusion of New Zealand, Vietnam and South Korea. Their inclusion has been considered a buy-in of the FOIP concept.[20]
QUAD Effects
The Quad enhances integrated deterrence by being a forum for the members of the Quad countries to meet and discuss measures on “…standard-setting, diplomatic messaging, and practical economic measures… to sustain a liberal rules-based order” and “build interoperability and other forms of military cooperation.”[21] At the Quad Foreign Ministers’ Meeting held in Washington, DC on July 1, 2025, the Quad members announced several “key initiatives” in the areas of maritime and economic security, critical and emerging technology, and support for humanitarian assistance and emergency response across the region.[22] They also announced the Quad Critical Minerals Initiative, a program to coordinate measures to provide a robust supply chain and to diversify it, an attempt to counter China’s control of the majority of critical minerals for lithium-ion batteries and electronics.[23]
One of the Quad’s main goals is to strengthen maritime security for the member states, and to this end, it implements the Indo-Pacific Partnership for Maritime Domain Awareness (IPMDA). Its goal is to enhance Indo-Pacific nations’ abilities to maintain maritime security by increasing their domain awareness at sea, monitoring for “illicit maritime activities…, climate events, and humanitarian crises.”[24] It offers training and access to new technology to enable surveillance of its territorial waters. It also plays a role in integrated deterrence by involving government agency support. For example, in December 2025, the US Navy had recently renewed its contract for the “Hawkeye 360’s commercial radio frequency (RF) data and analytics for vessel detection and monitoring.”[25] The US Navy also shares this data with its partners under IPMDA, such as India. The US Navy worked with the Indian Navy and the Indian Ministry of External Affairs to help tailor how Hawkeye 360 will help Indian maritime security, and the US Navy also coordinated with the “US Department of State, the Defense Security Cooperation Agency, Navy International Programs Office, and other interagency partners” to request US government approval to offer a new and improved capabilities to India in support of IPMDA.[26] Data-sharing is particularly sensitive for any national government to do, so India being granted Western-based data highlights the trust showcased, especially in the absence of a formal alliance structure.[27] Other measures in support of maritime security are the Quad-at-Sea Ship Observer Mission. On 25 June 2025, coast guard personnel from the Quad were assigned to the US Coast Guard cutter Stratton in support of the FOIP concept.[28] Its mission was to support interoperability and build trust amongst nations.
While maritime security might be the Quad’s centerpiece, it has also encouraged joint operations on humanitarian aid, cyberwarfare, and other critical technologies, such as communications. The Quad strengthens integrated deterrence by signaling the Quad members’ interoperability in times of crisis, while working on strengthening critical infrastructure. An analysis of the Quad’s activities and announcements showcased that although the members may have different national strategic goals and operational capabilities, they found common cause in the FIOP concept, and by pooling assets and state ability, the Quad countries strengthen integrated deterrence amongst each other.
Case 2: The I2U2 Group
Despite American interest in the Middle East, the Middle East is mostly anti-Americanist. However, there are some states such as Israel and the United Arab Emirates (UAE) that maintain friendly relations with the US, especially with security ties. Mohammed Soliman, in an essay for the Middle East Institute, argues that India, Israel, and the UAE have “shared anxieties” of “Islamist movements to Tehran’s and Ankara’s expansionist foreign policy.”[29] By 2020, Tel Aviv and Abu Dhabi (along with Bahrain) had normalized relations with the signing of the Abrahamic Accords and had begun security and “emerging technologies and cyber capabilities” cooperation.[30] Joint military exercises have occurred, and the Israeli government has dropped its opposition to the UAE acquiring F-35 stealth fighter jets.[31] For its part, India has a cold and often hostile relationship with Pakistan. Pakistan has a major ally with China and has been supportive of Ankara’s foreign policy. Personal relations between Turkish President Erdoğan and Indian Prime Minister Modi have also been cold. New Delhi and Tel Aviv were also concerned with Islamist movements and have defense ties as well. Soliman argues that these three countries can form a geopolitical bloc, a “Indo-Abrahamic alliance” with a “potential to transform the region’s geopolitics and geoeconomics” and provides the United States an opportunity to shore up American presence in the Middle East.[32]
On October 18, 2021, the foreign ministers of India, Israel, the UAE, and the US held a virtual meeting, and on July 14, 2022, these states formed the I2U2 Group. Unlike the more security-oriented Quad, the I2U2 Group instead focuses on NTS issues, such as “joint investments and new initiatives in water, energy, transportation, space, health, food security, and technology.”[33] In matters of space, all the states are signatories to the Artemis Accords, a series of non-binding treaties for space exploration, and in 2021, the I2U2 Group announced a new “space-based tool” for the greater good of humanity.[34] It has also invited states to existing initiatives, inviting India to the UAE-US Agricultural Innovation Movement for Climate Initiative (AIM for Climate). AIM for Climate’s goal is to combat the impact of climate change on farms by “investment in and support for climate-smart agriculture and food systems innovation over five years (2021 – 2025), addressing both climate change and global hunger.”[35] In an example of integrated deterrence, in the area of clean energy, the US Trade and Development Agency funded a feasibility study on a wind and solar hybrid renewable energy project in India’s Gujarat State, promoting clean energy with Indian enterprises and UAE-based companies’ intellectual experience on the matter.[36]
Although not defense oriented, the I2U2 Group contributes to deterrence by denial by making it difficult for an adversary to compel compliance by reinforcing member states’ critical infrastructure such as food security and the cyberspace domain. Aprana Pande, writing for the Hudson Institute, writes that the I2U2 has “tremendous geopolitical and geoeconomic promise.” Pande noted American interest in West Asia is strongly tied to its minerals and oil, but also notes a role in growing business in the region and to outcompete China by leveraging technology, especially Israeli technology.[37]
Yet, in recent times, there has been no new news nor updates from the I2U2 Group. The Jerusalem Post has written that Israel should do more as part of the group.[38] The US State Department page on the I2U2 Group is sparse on activities. The 2023 Gaza War has led to tensions between the UAE and Israel, and “India has adopted a ‘wait and watch’ approach.”[39] American interest in the region since 2025 has been shifted to providing political and material support of Israel, and recently has signaled disinterest in NTS issues, given its massive budget cuts in soft power measures, diplomacy and scientific measures.[40] There may be signs that Washington would be stepping away from the I2U2 Group and focusing instead on bilateral relations as the US deepens its ties with Saudi Arabia and Qatar instead.[41]
This lack of interest, or the lack of signaling, highlights that the strength of informal alliances, forming groups based on interest without legal and formal structures, is also a weakness if the interest cannot be sustained. While the I2U2 Group was “active” it helped provide integrated deterrence for American allies, but currently the Group is simply a footnote. But perhaps like the Quad, where its resurgence was caused by China’s more aggressive foreign policy, the I2U2 Group might see a resurgence if Ankara or Tehran makes a bold move.
Case 3: American–Japanese–Korean Trilateral Pact
Returning to East Asia, Japan and South Korea are both major American security partners, share similar security concerns regarding China and North Korea (DPRK), and the relatively short distance between each other should make them good allies.[42] Unfortunately, the specter of the Asia-Pacific War cast a long shadow over any form of positive relations between them. Japan, despite an acknowledgment of the pain of war, may be ambiguous on the cause of war or even deny war crimes. Controversy arises from Japan’s perceived unapologetic nature over its war past, such as the textbook revisions to remove mentions of war crimes and the visits of high government Japanese officials to Yasukuni Shrine, which are controversial in China and Korea due to the enshrinement of convicted war criminals by the Tokyo War Crimes Tribunal, and South Korea’s insistence on Japanese reparations on the comfort woman issue. South Korea may also be hesitant to pursue closer relations with Japan due to China, the largest trade and economic partner with South Korea, who also has negative views of Japan’s treatment of the war history. A subject matter expert knowledgeable in Japan-South Korea military affairs has mentioned the difficulties in having Japan and South Korea work together in security matters, and they only do so if it is American-led or supported, even if there are many benefits for a Japanese-South Korean alliance.[43] Yet, despite their shared animosity, international events would bring them together. In 2017-2018, North Korean nuclear saber-rattling, and the launches of missiles over Japan, along with a more proactive China in the 2020s and the Russian invasion of Ukraine in 2022, led South Korea and Japan to increase cooperation with each other. On August 18, 2023, the leaders of the US, Japan, and South Korea met in Camp David and announced the American–Japanese–Korean trilateral pact. It is a military alliance, but still relatively informal because it “lacks sufficient institutionalisation,” yet the “fundamentals are strong.”[44] In terms of integrated deterrence, the trilateral operates as a deterrence by denial. America has signaled that Japan and South Korea are still protected by its nuclear umbrella, and the three nations participated in high-level strategic consultations and in joint military exercises. A trilateral flight in January 2025, involving Japanese and South Korean jet fighters escorting American strategic bombers, demonstrates the ability to execute military interoperability in emergency situations.[45]
They have collaborated on a “real-time DPRK missile warning data sharing mechanism and a multi-year trilateral exercise plan.”[46] Japan and the US have agreed on a “cooperative acquisition” of armaments, such as collaboration among “industrial bases” and supply chains to produce armaments, such as “uncrewed aircraft and hypersonic interceptors.”[47] The Trilateral made pledges to work towards cooperation in cybersecurity, economic security and resilience, maritime security and law enforcement, and to support capacity building of ASEAN member states.[48]
As there is no alliance between Japan and South Korea themselves, the Trilateral has provided high level discussions so that in an emergency, there is a prepared plan instead of an ad hoc response. They also created a Trilateral Coordinating Secretariat to streamline the works, in a bid to “institutionalize” the trilateral to a more formal framework to continually generate American interest.[49] By this, the Trilateral has produced clear signaling of the FOIP concept, and its nature as a less formal alliance, has allowed South Korea and Japan to work together, in the absence of a formal security treaty or alliance between the two nations.
Like any informal alliance, it does have its issues. Namely, American fears of being dragged into a war not of its own choosing. Its fears manifested by its refusal to grant Japan counterstrike capability by limiting intelligence sharing. Counterstrike capability is the ability to return a strike after receiving a strike. Currently (2025), Japan does not have the ability to carry out a counterstrike independently, and has historically relied on the Americans for counterstrike capability. As there are fears that American disinterest in the area would lead to abandonment of the alliance, Japan may need to develop its own independent counterstrike capabilities. Despite the alliance, the partnership between the three is relatively unequal, for example, Admiral (ret.) Tomohisa Takei of the Japan Maritime Self-Defense Force (JMSDF), has discussed how America’s worldwide naval deployments have stressed both crew and vessels. With American shipyards unable to respond to that need due to lack of capability, Admiral Takei said that Japanese shipyards could assist in the maintenance, repair and overhaul (MRO) of American naval ships.[50] Yet, the Americans are unwilling, enshrining in US law that American naval vessels may not be serviced outside the US or Guam.[51]
Despite these shortcomings, the Trilateral provides integrated deterrence by providing coordination in the military and maritime security realm, and in the fields of economic resiliency, cybersecurity and cooperation. With the US having issues with naval warship procurement, and recently cancelling the Constellation-class frigate project in November 2025, perhaps America could deepen its ties with both South Korea and Japan by working out a plan to standardize parts and repair processes for the overhaul of naval vessels.[52] Such deeper coordination would be more power signaling and can still work in the confines of an informal alliance if necessary.
Conclusion
America and its allies needed to contend with many things, competition with China and Russia, along with many non-traditional security issues. Therefore, there is a desire to avoid negative effects by maximizing the effects of deterrence or hardening their state infrastructures against war and NTS, using integrated deterrence. Integrated deterrence is not only about military deterrence, but also about making the non-traditional security realms more resilient, such as the economic supply chain. As formal alliances, involving legally binding treaties, may have significant political hesitation, and may prove limiting or not as agile, led to the rise of minilateralism and informal alliances. These informal alliances, such as the Quad, the I2U2 Group, and the Trilateral Pact, have encouraged the US and its partner states to work closer in the military and the NTS realms. By adopting the tenets of integrated deterrence, though not the language, these informal alliances have strengthened integrated deterrence by having different states work towards common goals.
Yet, times are changing, despite the helpfulness of these alliances, the US under the second Trump Administration is distrustful of international cooperation and is now willing to support a “world order” by might makes right, a sentiment shared by China and Russia. In 2025, Washington had instituted tariffs to nearly all trade goods entering the US; strained both NATO and EU relations by threatening to annex Greenland from Denmark; and in early 2026, ordered a military operation in Venezuela that ended in the capture of President Nicolás Maduro for trial in the US. While the international and domestic ramifications are still to be determined, it has demonstrated American (or at least the Trump Administration’s) distrust and repudiation of both formal and informal alliances, and even international law as well, in favor of self-reliance. Nations may reconsider partnership with the US in light of these events, and may either spell the end of these US-led formal and informal alliances, or kickstart a new wave of alliances without US involvement, perhaps even as a defense against the US, a significant policy change for some nations.
Wilson Tang is a graduate student and a member of the Indo-Pacific Policy Lab at the University of Hawai‘i at Mānoa.
The views expressed in this publication are those of the author and do not necessarily reflect the position of the Center for Indo-Pacific Affairs or any organization with which the author is affiliated.
© 2026 University of Hawai‘i at Mānoa Center for Indo-Pacific Affairs. All rights reserved.
[1] Michael J. Mazaar, Understanding Deterrence, RAND, April 19, 2018, 2.
[2] Ibid., 2.
[3] Ibid., 2.
[4] Ibid., 3.
[5] Ibid., 3.
[6] Erik Gartzke and Jon Lindsay, “The U.S. Department of Deterrence,” War on the Rocks, July 22, 2024
[7] Department of Defense, 2022 National Defense Strategy of the United States of America, US Government, October 2022, III.
[8] Ibid., 8.
[9] Rebecca Shrimpton and Iain MacGillvray, “Integrated Deterrence,” in ‘With a Little Help From My Friends’: Capitalising on Opportunity at AUSMIN, November 1, 2022, 43.
[10] Philip Kapusta, The Gray Zone, US Special Operations Command, October–December 2015, 20.
[11] Patrick Gerard Buchan and Benjamin Rimland, Defining the Diamond: The Past, Present, and Future of the Quadrilateral Security Dialogue, Center for Strategic and International Studies (CSIS), March 2020, 2.
[12] Ibid., 2.
[13] Ibid., 3.
[14] Lavina Lee, Assessing the Quad: Prospects and Limitations of Quadrilateral Cooperation for Advancing Australia’s Interests, Lowy Institute, May 2020, 1.
[15] Roland Rajah, Alexandre Dayant, and Jonathan Pryke, Ocean of Debt?: Belt and Road Debt Diplomacy in the Pacific, Lowy Institute, October 2019, 2–7.
[16] Buchan and Rimland, Defining the Diamond, 4.; Nuclear Suppliers Group, “About the NSG.”
[17] Department of Defence, 2016 Defence White Paper, Australian Government, 2016, 30.
[18] Ibid., 70.
[19] Ministry of Foreign Affairs of Japan, “Japan-U.S. Working Lunch and Japan-U.S. Summit Meeting,” Japanese Government, November 6, 2017.
[20] Jeffrey Reeves, Canada and the Indo-Pacific: ‘Diverse and Inclusive’, not ‘Free’ and ‘Open’, Asia Pacific Foundation of Canada, September 2020, 34.
[21] Lee, Assessing the Quad, 3.
[22] Office of the Spokesperson, “2025 Quad Foreign Ministers’ Meeting,” US Department of State, July 1, 2025.
[23] Ibid.
[24] Department of the Prime Minister and Cabinet, “Indo-Pacific Partnership for Maritime Domain Awareness,” Australian Government, 2023.
[25] Seapower Staff, “Navy Renews HawkEye 360 Contract to Advance Indo-Pacific Maritime Domain Awareness,” Seapower Magazine, December 16, 2025.
[26] Naval Information Warfare Center Pacific Public Affairs, “NIWC Pacific Enhances India’s Maritime Security Capabilities,” US Navy, May 22, 2025.
[27] Peter Parson, “Quad’s Maritime Domain Awareness Initiative Strengthens Indo-Pacific Security,” Indo-Pacific Defense Forum, June 19, 2025; Pratnashree Basu, “Why Maritime Surveillance in the Indo-Pacific Starts with Trust Before Data,” The Interpreter, Lowy Institute, August 21, 2025.
[28] Japan Coast Guard, “First Ever a Quad-at-Sea Ship Observer Mission Conducted by Coast Guard of Member Countries the Framework of Japan-Australia-India-U.S. ～To Realize a ‘Free and Open Indo-Pacific～,” July 23, 2025.
[29] Mohammed Soliman, “An Indo-Abrahamic Alliance on the Rise: How India, Israel, and the UAE are Creating a New Transregional Order,” Middle East Institute, July 28, 2021.
[30] Mohammed Soliman, “How Tech is Cementing the UAE-Israel Alliance,” Middle East Institute, May 11, 2021.
[31] Dan Williams and Mike Stone, “Israel Will Not Oppose U.S. Sale of F-35 to UAE,” Reuters, October 23, 2020.
[32] Mohammed Soliman, “An Indo-Abrahamic Alliance on the Rise: How India, Israel, and the UAE are Creating a New Transregional Order,” Middle East Institute, July 28, 2021.
[33] Department of State, “I2U2: India, Israel, United Arab Emirates, United States,” US Government.
[34] Ibid.
[35] AIM for Climate, “About AIM for Climate.”
[36] Ministry of External Affairs, “Joint Statement of the Leaders of India, Israel, United Arabs Emirates and the United States (I2U2),” Indian Government, July 14, 2022.
[37] Aparna Pande, “The Trans-Regional Benefits of I2U2 for the US,” Hudson Institute, March 4, 2023.
[38] Lauren Dagan Amoss, “From Abraham Accords to I2U2: Why India Must do More with India, UAE, – Analysis,” The Jerusalem Post, September 16, 2025
[39] Amiti Sen, “Israel-Hamas Conflict Casts Shadow on Future of I2U2 Group,” The Hindu Business Line, August 30, 2024.
[40] Brian Katulis, “US Policy in the Middle East: Second Quarter 2025 Report Card,” Middle East Institute, July 31, 2025.
[41] Brian Katulis, “A Midstream Appraisal of Trump’s Historic Middle East Trip,” Middle East Institute, May 14, 2025.
[42] Kevin J. Cooney and Alex Scarbrough, “Japan and South Korea: Can These Two Nations Work Together?,” Asian Affairs: An American Review 35 (3), Fall 2008, 173–192.
[43] Author’s group discussion with subject matter experts.
[44] Ju Hyung Kim, “Why the US–Japan–South Korea Trilateral Agreement Must Evolve,” The Interpreter, Lowy Institute, October 13, 2025.
[45] Defense News Aerospace, “Breaking News: Japan – South Korea – US Conduct First Strategic Trilateral Escort of B-1B Bombers in Indo-Pacific,” Army Recognition Group, January 15, 2025.
[46] Ministry of Defense, “Joint Statement of the 14th Defense Trilateral Talks (DTT),” Japanese Government, April 24, 2024.
[47] Gregg Rubinstein, “Cooperative Defense Acquisitions Strengthen U.S.-Japan Alliance,” CSIS, January 30, 2025.
[48] Office of the Spokesperson, “Joint Statement from the Trilateral Meeting of the United States of America, Japan, and the Republic of Korea in New York City,” US Department of State, September 22, 2025.
[49] Akihisa Ota, “Japan, U.S., ROK to Set up Trilateral Secretariat to Ensure Cooperation; Ishiba, Biden Affirm Commitment to Alliance,” The Japan News, November 16, 2024.
[50] Tomohisa Takei, “How Should Japan Act in Enhancing Regional Security and Deterrence in the Advent of New Global Reality?,” presentation at the University of Hawaiʻi at Mānoa, October 8, 2025
[51] Moyuru Tanaka, “Navigating the Competitive Seas,” CSIS, August 13, 2024.
[52] Ibid.