How the US, Japan, and the Philippines are Building a New Alliance

How the US, Japan, and the Philippines are Building a New Alliance

Imagine this: A lone Philippine coast guard vessel 
crests a wave in the South China Sea at dawn, salt spray glinting in the early light. Its 
mission is routine – resupply a handful of marines living on a rusting World War II-era ship 
deliberately grounded on a remote shoal. Suddenly, a white hull looms on the horizon – a China 
Coast Guard cutter nearly three times its size. A blaring siren and flashing lights accompany 
the cutter’s approach. Without warning,   a powerful water cannon erupts, pummeling 
the Philippine boat. Crewmen stagger as the torrent shatters the bridge windows; equipment 
is knocked out and injuries are reported. The small vessel rolls helplessly in the onslaught, 
its radios sputtering. Now imagine that scene playing out differently next time: Flanking 
the Philippine boat are allied ships from   Japan and the United States, their presence 
a clear signal to the bully on the horizon. The water cannons fall silent. The standoff 
ends before it begins. How did this nimble, powerful bloc come together to contain China’s 
maritime ambitions? How did the United States, Japan, and the Philippines form an “Iron Triangle” 
alliance to push back in the South China Sea? For years, the balance of power in Asian waters 
has been shifting – and not in favor of smaller nations. China’s growing maritime assertiveness 
has fundamentally altered the strategic landscape in the Indo-Pacific. It has built and militarized 
artificial islands atop coral reefs in the South China Sea, deploying runways, radars and 
missiles where once only turquoise waters lay. Heavily armed Chinese coast guard and 
“maritime militia” vessels now patrol disputed areas incessantly, challenging the sovereignty 
of other claimants. In the East China Sea, Chinese ships circle Japanese-administered islets; 
in the Taiwan Strait, Chinese warplanes test their neighbors’ air defenses. And in the South China 
Sea – including waters internationally recognized as the Philippines’ exclusive economic zone – 
Beijing asserts ownership through its expansive “nine-dash line” claim, a claim invalidated 
by an international tribunal in 2016 but still aggressively enforced by China on the water.
Why does this moment matter? Because Beijing’s actions have set off alarm bells across the 
region. The South China Sea is strategically vital, with roughly $3 trillion in goods shipping 
through each year, and is rich in fish and potential energy reserves. By fortifying 
positions and harassing foreign vessels, China seeks to make its de facto control a fait 
accompli. For countries like the Philippines, this trend strikes at both national pride and 
economic livelihood – its fisherfolk are chased from their own fishing grounds, its offshore 
oil/gas prospects stalled by intimidation, and its Navy outposts beleaguered. Philippine 
ships have routinely been shadowed and harassed by China’s coast guard in areas like Scarborough 
Shoal and Second Thomas Shoal, within waters the Philippines claims by law. Each incident has 
been pushing Manila closer to a crossroads: accept a new era of diminished maritime 
rights, or push back with help from friends. Compounding the urgency, the Philippines’ 
strategic posture has whiplashed in recent   years. Under former President 
Rodrigo Duterte (2016–2022), Manila tried a conciliatory approach 
to Beijing, downplaying the 2016 legal victory and distancing itself from its U.S. 
ally. The result? Minimal Chinese investment, continued militarization, and unabated bullying 
at sea. By contrast, the current president, Ferdinand “Bongbong” Marcos Jr., has pivoted 
sharply. Since taking office in mid-2022, Marcos Jr. has reinvigorated the U.S. alliance and 
sought new security partners. This policy U-turn set the stage for a trilateral alignment 
few would have imagined a decade ago: one that brings together America’s oldest Pacific 
ally (the Philippines), its most powerful Asian ally (Japan), and the United States itself. 
Each leg of this emerging triangular security alliance has its own reasons for concern 
– and now, at last, they are linking arms. If long-term trends provided the kindling, 
China’s recent maritime aggression was the   spark that ignited the “Iron Triangle.” A 
series of provocations in 2023–2024 jolted the Philippines into action and crystallized the 
need for tighter cooperation with Washington and Tokyo. Perhaps the most galvanizing incidents 
have been China’s brazen use of force against Philippine vessels – in peacetime and 
within the Philippines’ own waters. In February 2023, a Chinese coast guard ship aimed 
a “military-grade” laser at a Philippine patrol boat near Second Thomas Shoal, temporarily 
blinding crew and causing outrage in Manila. The Philippine leadership’s response marked a 
turning point. Rather than quietly protest through diplomatic notes (the old approach), President 
Marcos Jr. ordered the release of photographs of the laser attack to the media. “The public 
deserves to know,” his national security adviser decided in an emergency meeting. And so began 
a campaign of “transparency” – exposing Chinese actions to sunlight. It was a calculated move to 
raise international awareness and “impose severe costs on Beijing’s reputation” for its behavior.
From that point on, each Chinese provocation only steeled Manila’s resolve further. In August 2023, 
for example, Chinese ships blocked and blasted a Philippine resupply boat with water cannon, 
preventing it from reaching the dilapidated BRP Sierra Madre outpost at Second Thomas Shoal. Video 
of the incident – a powerful jet of water arcing from a Chinese vessel, slamming into the smaller 
Philippine boat – was released to the world, sparking global condemnation. U.S. officials 
denounced the “dangerous actions” and reaffirmed that any attack on Philippine public vessels 
(yes, even a coast guard or supply boat) would invoke the U.S.-Philippines Mutual Defense 
Treaty. Japan’s government, for its part, blasted the use of water cannons as “undermin[ing] 
the safety of ship and crew” and explicitly opposed any actions escalating tensions. Such 
statements of support were not lost on Manila. Then came the ramming incidents. In 
a highly alarming clash in June 2024, dozens of Chinese coast guard personnel 
– some wielding knives and axes – rammed a Philippine Navy boat during another Second 
Thomas Shoal resupply run. The melee resulted in one Filipino sailor losing a finger, marking 
the most violent skirmish in the area in years. Around the same time, Chinese ships were recorded 
placing a floating barrier to block Filipino fishermen from entering Scarborough Shoal’s lagoon 
(another rich fishing area grabbed by China in 2012). In late 2023, near Scarborough, a Chinese 
vessel even collided with a Philippine boat, with each side trading accusations over the cause. 
These episodes drove home a frightening point: left unchecked, China’s “gray-zone” 
harassment could turn deadly,   whether by accident or design. “A fatal accident 
could escalate into open hostilities,” Philippine Ambassador Jose Manuel Romualdez warned – 
“that keeps a lot of us awake at night”. Crucially, each act of Chinese belligerence 
served to strengthen Manila’s determination   to bolster alliances. Every water cannon 
attack or hull scrape made headlines and underscored the imbalance the Philippines faced 
alone. Marcos Jr.’s government deftly used these incidents to rally international support. They 
invited foreign journalists onboard their ships to document confrontations, and a Philippine 
coast guard spokesman began regularly taunting China on social media with video evidence of 
Chinese aggression. This transparency policy, as intended, garnered sympathy and statements 
of solidarity from many nations – not only the U.S. and Japan, but also Australia, India, 
several European countries, and ASEAN neighbors. Most importantly, the Philippines reached out 
directly to its two closest security partners. In early 2023, just days after the laser incident, 
President Marcos granted the U.S. military access to four additional Philippine bases – a major 
expansion of the countries’ defense pact that had stalled under Duterte. These new sites 
would allow U.S. forces to rotate through strategic locations in the north and west of the 
Philippines, including one near the contested Spratly Islands and others facing Taiwan. Marcos 
also made high-profile visits to Washington and Tokyo to reaffirm security ties. In a historic 
first, on April 11, 2024, the leaders of the Philippines, Japan, and the U.S. met together in 
a trilateral summit at the White House. There, President Biden reiterated America’s “ironclad” 
commitment to Philippine defense, and all three leaders agreed to “bolster maritime cooperation” 
in the face of China’s actions. What had been a loose idea of trilateral coordination suddenly 
became tangible: the Iron Triangle was beginning to take shape. Beijing, notably, took angry notice 
of “this emerging triangle,” calling it aimed at China – a telling sign that the new coalition 
was already being felt in Beijing’s calculus. Perhaps the most remarkable element of this 
trilateral alignment is the role of Japan. After World War II, Japan famously adopted a 
pacifist constitution; for decades, it maintained only Self-Defense Forces (SDF) with a strictly 
defensive mandate and foreswore any overseas military engagements. Japanese politicians often 
avoided even the appearance of joining foreign conflicts. Yet today, Japan is shedding elements 
of that postwar pacifism and stepping forward as a key security partner in Southeast Asia – 
including areas far from its home waters. How did this happen? In short, China’s rise and regional 
provocations have compelled Tokyo to redefine its strategic posture, and the Philippines’ plight 
has resonated strongly with Japanese leaders. It starts with Japan’s own security environment. 
In Northeast Asia, Tokyo faces twin threats: an aggressive North Korea testing missiles, and 
a territorially assertive China pressing claims to the Senkaku Islands (administered 
by Japan in the East China Sea). Chinese coast guard ships and aircraft intrude 
around the Senkakus on a near-daily basis, in what Japan views as an effort to erode its 
control. Japan knows well the kind of pressure the Philippines faces. As one analysis put it, 
Japan is “deeply familiar” with the challenges to sovereignty that constant Chinese incursions pose. 
Moreover, any conflict over Taiwan (which lies between Japan and the Philippines) would almost 
certainly involve Japan. This shared strategic concern – maintaining a rules-based order against 
Chinese revisionism – has drawn Tokyo, Manila, and Washington into closer alignment.
In response to growing threats,   Japan has undertaken a landmark military buildup 
and policy shift in recent years. In late 2022, Tokyo approved new security strategies that 
include doubling defense spending to 2% of GDP within five years and acquiring longer-range 
strike capabilities – moves once unthinkable for the officially pacifist nation. It also loosened 
decades-old restrictions on defense exports and military cooperation. Under former Prime Minister 
Shinzo Abe and his successors, Japan has embraced the concept of a “Free and Open Indo-Pacific” and 
recognized that its own security is intertwined with that of its neighbors. Japan’s emergence as 
a proactive security partner has been striking. In fact, Japan quickly became “one of the 
Philippines’ most important security partners” as well as an economic partner. This is a sea change: 
within living memory, Japan was the invader of the Philippines; now it is providing ships and 
planes to help the Philippines defend itself. Concrete steps in the Japan-Philippines security 
relationship illustrate this pivot. As early as the 2010s, Japan started transferring 
maritime assets to the Philippines: it provided ten brand-new Coast Guard patrol 
vessels to the Philippines on concessional terms and leased TC-90 surveillance aircraft to 
help the Philippine Navy patrol its seas. These were significant departures from Japan’s 
previous self-imposed limits. In 2013, after Typhoon Haiyan struck the Philippines, Japan 
sent an SDF disaster relief mission – its first major deployment of forces overseas since WWII, 
albeit for humanitarian aid. Tokyo also supported peacebuilding in the southern Philippines 
(Mindanao), putting “boots on the ground” in a   non-combat role for the first time in a conflict 
zone. Each of these steps built confidence and familiarity between Japanese and Filipino forces.
Then, in April 2023, Japan launched a new program called Official Security Assistance (OSA) – 
essentially, grant aid for defense equipment to like-minded countries. The Philippines was a 
top priority. Through OSA, Japan moved to donate a state-of-the-art air surveillance radar system 
to the Philippines to bolster its monitoring of the West Philippine Sea. By the end of 2024, 
Tokyo earmarked additional radars and at least ¥1.6 billion (over $10 million) in security aid 
to Manila, including coastal radar systems and inflatable boats to enhance Philippine maritime 
patrols. These are relatively modest sums, but symbolically powerful – Japan is directly 
enhancing another nation’s military capabilities to check Beijing’s moves. “Japan’s first 
international defense sale following landmark reforms was radars for the Philippines,” 
analysts note, highlighting Manila as a proving ground for Tokyo’s more assertive posture.
Most dramatically, Japan and the Philippines agreed to a Reciprocal Access Agreement (RAA) 
– a legal framework allowing their forces to deploy on each other’s soil for joint training and 
exercises. This pact, signed by both governments in mid-2024, is Japan’s first such agreement 
with any Asian country (its only other RAAs are with Australia and the UK). In December 2024, the 
Philippine Senate unanimously ratified the RAA, with senators openly citing China’s “increasingly 
assertive stance” as the impetus. By June 2025, Japan’s Diet (parliament) completed its 
ratification as well. The RAA “will ease the entry of equipment and troops” for everything 
from combat drills to disaster relief, smoothing military cooperation. In essence, it paves the 
way for Japanese troops to train on Philippine territory for the first time since World War II 
– a full-circle moment of historic significance. Japanese Prime Minister (at the time) Fumio 
Kishida welcomed the RAA, seeing the Philippines as a vital partner in a volatile region. Indeed, 
Tokyo’s growing network of security ties – long anchored by the U.S.-Japan alliance – now 
increasingly extends southward to nations   like the Philippines, Australia, and Vietnam.
Japan’s pivot has not been without domestic debate – many Japanese remain cautious about 
entanglement in distant conflicts – but there is broad recognition in Tokyo that standing 
up to coercion in the South China Sea today may prevent a larger conflagration tomorrow. As 
Japan’s ambassador to Manila put it recently, Japan “upholds the rule of law and opposes any 
actions which increase tensions” in regional waters. By arming and training with the 
Philippines, Japan is effectively pushing back against China’s attempt to carve out a 
sphere of influence through force. In doing so, Japan fortifies not only the Philippines’ defenses 
but also its own, since a more secure Southeast Asia contributes to “a stable region amid China’s 
aggression,” which is exactly what Washington, Tokyo, and Manila are jointly aiming for.
From Drills to Deterrence  What does this burgeoning trilateral alliance 
look like in action? By mid-2025, it has moved beyond strategic pledges and into real-world 
operations on, above, and around the waters of the Philippines. Through joint exercises, expanded 
base access, and coordinated patrols, the U.S., Japan, and the Philippines are translating 
their partnership into a tangible deterrent presence. The message to Beijing is clear: any 
further adventurism will not go unanswered. One of the earliest visible fruits of the 
alliance was a series of joint military   drills and exercises. In June 2023, as tensions 
simmered, the three countries’ coast guards launched their first-ever trilateral maritime 
exercises off the coast of Bataan, Philippines. In one dramatic simulation, Philippine coast 
guard personnel – backed by American and Japanese counterparts – boarded a vessel in a mock 
operation to intercept contraband weapons, facing down “armed” adversaries in the drill. The sight 
of Philippine, U.S., and Japanese ships and small boats maneuvering together was unprecedented. 
Over 500 coast guard personnel took part, practicing search-and-rescue, law enforcement, 
and anti-piracy scenarios. The symbolism was as important as the tactics: three flags flying 
side by side on the high seas, training to help each other. “All the exercises we do, we help one 
another prepare for anything that may happen in the future,” a Philippine coast guard spokesperson 
explained. Japan and the U.S., he noted, hav e been providing ships and training, and now 
were seeing how much the Philippines had improved. Members of the Philippine Coast Guard aboard the 
BRP Melchora Aquino participate in a trilateral coast guard exercise with Japan and the 
U.S. off Bataan, June 2023. Such joint drills aim to enhance search-and-rescue, 
law enforcement, and interoperability amid China’s expanding maritime presence.
These exercises quickly ramped up in scope. In 2024 and 2025, the annual U.S.-Philippines 
“Balikatan” wargames (already one of Asia’s largest military drills) grew even larger – and 
for the first time, included Japanese troops. Balikatan 2023 saw some 17,600 troops (American 
and Filipino) conducting live-fire exercises, coastal defense simulations, and even a 
boat-sinking exercise, in a show of force meant to reassure the Philippines and warn China. 
By Balikatan 2025, at least 17,000 personnel were involved, now with hundreds of Japanese (and 
Australian) forces participating directly in combined operations. This multilateral dimension 
– Japan and Australia fighting side-by-side with U.S. and Filipino forces on Philippine 
soil – would have been hard to imagine just a few years ago. It demonstrated a new level of 
interoperability. In one 2024 drill, allied troops practiced an amphibious landing and air assault 
to retake an island, a scenario not-so-subtly reminiscent of repelling a forcible seizure of a 
Philippine-claimed shoal or island. Furthermore, for the first time, joint naval maneuvers 
were held inside the Philippines’ exclusive economic zone during Balikatan 2024. The clear 
subtext: we will jointly operate in these waters, and China’s unlawful claims won’t stop us.
Parallel to these exercises, the U.S.-Philippine alliance has deepened its integration through 
the Enhanced Defense Cooperation Agreement   (EDCA) – now supercharged to support the new 
triangle. EDCA, originally signed in 2014, allows U.S. forces to rotate through and pre-position 
materiel at designated Philippine bases. For years it languished, but under Marcos Jr. it sprang 
to life. In 2023, the Philippines increased EDCA sites from 5 to 9, granting U.S. access 
to key locations: bases in northern Luzon (near Taiwan) and Palawan (facing the Spratly Islands) 
among others. These sites are being upgraded with U.S. funding – over $100 million committed 
– to store defense equipment, build runways, port facilities, and training infrastructure. 
Already, U.S. military presence in the Philippines is the highest in decades, albeit still on a 
rotational (not permanent basing) basis. American fighter jets and naval patrol planes have begun 
operating out of Philippine airfields on temporary deployments, significantly cutting response times 
to any South China Sea flare-up. U.S. Coast Guard cutters have also conducted training and 
patrols alongside their Philippine and   Japanese counterparts, blurring the line between 
exercises and real-world deterrence patrols. Another concrete manifestation of the trilateral 
alliance is joint patrols in contested waters. In late 2023, after a particularly dangerous Chinese 
maneuver that led to a collision with a Philippine boat, the Philippines for the first time invited 
allied navies to patrol together in the West Philippine Sea (the Philippine term for its 
part of the South China Sea). By November 2023, Philippine, U.S., Japanese (and even Australian) 
vessels sailed in formation on a joint patrol near Scarborough Shoal – a flashpoint area about 
120 nautical miles off Luzon that China has controlled since 2012. The united patrol sent a 
strong signal: it upheld the “right to freedom of navigation and overflight” in those waters and 
pushed back against China’s unilateral assertions. Notably, a U.S. Navy P-8 Poseidon aircraft 
provided overwatch while a Japanese destroyer and Philippine vessels patrolled below. Although 
these were limited patrols, they are expected to become more regular. U.S. National Security 
Adviser Jake Sullivan confirmed in April 2024 that “more joint patrols can be expected in the 
South China Sea” following combined drills by the four countries. The strategic logic is simple: 
when Chinese ships know they might face not just the Philippine Coast Guard, but also U.S. and 
Japanese naval power, their calculus changes. Beyond patrols and drills, the trilateral 
cooperation extends to capability-building and infrastructure support that strengthen deterrence. 
Japan’s contribution here is noteworthy. Tokyo provided the Philippines with 
four advanced coast guard radar systems,   enabling better maritime domain awareness, 
and has trained hundreds of Philippine Coast Guard personnel. It also transferred freezer 
containers and dredging equipment to improve the living conditions and maintain the 
sandbar at the Sierra Madre outpost – small things that help the Filipinos hold their 
ground at Second Thomas Shoal. Meanwhile, the United States has been helping upgrade 
Philippine military facilities under EDCA,   constructing warehouses, command centers, and 
training ranges that will allow rapid deployment of forces in a crisis. Washington also increased 
Foreign Military Financing to the Philippines, facilitating the purchase of new surveillance 
drones, helicopters, and coastal defense missiles. And in a truly joint endeavor, Japan and the U.S. 
are coordinating on technology and infrastructure projects for the Philippines – for instance, 
exploring how to network Philippine coastal radars with Japanese and American systems for a unified 
picture of Chinese ship movements. There’s also talk of involving the Philippines in AUKUS-related 
technology cooperation, such as maritime drone development, indicating the triangle is 
plugging into broader regional initiatives. All these efforts – exercises, patrols, 
base access, arms aid – add up to a strategy of deterrence by presence. The allies are 
operationalizing their alliance to convince Beijing that coercion will be met with collective 
pushback, not isolated protests. Already there are signs this is having an effect. Filipino officials 
observe that while Chinese harassment continues, it remains mostly at the “water cannon and 
blocking” level, as if Beijing is wary of crossing a line that would trigger U.S. intervention. 
“China has few escalatory options left without triggering the U.S.-Philippines defense treaty,” 
notes Ian Storey of ISEAS-Yusof Ishak Institute, given the new international spotlight and allied 
presence. In other words, the Iron Triangle may be starting to blunt China’s gray-zone tactics by 
raising the stakes. To maintain this deterrent effect, the three partners know they must keep up 
the tempo – continuing routinized drills, patrols, and planning. As a U.S. Institute of Peace brief 
put it, “the speed with which this triad has developed” is impressive, but now it must be 
sustained and made routine. If they succeed, a Chinese coast guard captain in the South China 
Sea will think twice before spraying that next water cannon or nudging his ship into a risky 
collision course, knowing it might provoke not just the Philippines, but a multi-nation response.
Comparative Perspective:   Why a ‘Minilateral’ Might Work
It’s worth asking: why pin hopes on a trilateral alliance? After all, there 
are larger multilateral groupings in the Indo-Pacific – notably ASEAN (Association of 
Southeast Asian Nations) and the Quad (U.S., Japan, India, Australia) – that also aim for 
regional stability. What makes this smaller “minilateral” pact potentially more agile 
and impactful than those broader forums? The answer lies in focus and cohesion. 
Sometimes, a tight-knit team with a clear mission can act faster and more decisively 
than a big committee trying to please everyone. Start with ASEAN, which includes the Philippines 
and nine other Southeast Asian states. ASEAN operates by consensus and emphasizes unity, but 
that very nature limits its ability to confront China. The organization has been negotiating a 
Code of Conduct with China for the South China Sea for over two decades, with little progress to 
show; any strong language is often watered down by members more aligned with Beijing’s views (e.g. 
Cambodia, Laos). Getting all 10 countries – from staunch U.S. ally Singapore to China-leaning 
Cambodia – to agree on robust collective action against Chinese maritime encroachments 
has proven nearly impossible. Indeed, aside from the Philippines, most Southeast Asian 
states still hedge between Washington and Beijing, avoiding firm alignment. Even Vietnam, which 
shares Philippine concerns about China, balances its new Comprehensive Strategic 
Partnership with the U.S. by simultaneously deepening ties with China. In this context, 
expecting ASEAN to jointly patrol the South China Sea or invoke mutual defense is unrealistic. 
By contrast, the U.S.-Japan-Philippines triad is a coalition of the willing – and the able. It 
sidesteps ASEAN’s internal divisions by uniting just the most forward-leaning players on this 
issue. As one commentator noted, Manila’s clear alignment with Washington and Tokyo is exceptional 
in Southeast Asia, and “other Southeast Asian states are not expected to follow suit” anytime 
soon. That’s precisely why this trilateral needed to form: to do what ASEAN as a whole cannot.
What about the Quad? The Quad (U.S., Japan, India, Australia) is another important minilateral 
which gets a lot of attention as a counterweight to China. It certainly has strategic weight – 
including India’s huge population and Australia’s geographical reach. However, the Quad’s scope 
is broader (covering everything from vaccines to infrastructure), and it lacks the tight focus 
on the South China Sea that the Iron Triangle has. India, in particular, has a more ambivalent stance 
on China’s maritime disputes in East Asia. New Delhi is locked in its own border standoffs with 
China in the Himalayas, but it has traditionally been reluctant to involve itself militarily in the 
South China Sea, partly to avoid provoking China and partly because its navy’s priority is the 
Indian Ocean. Thus, the Quad has not engaged in joint freedom-of-navigation patrols or collective 
security commitments in the South China Sea. Its members also have varying threat perceptions; 
for example, India’s and Australia’s immediate security concerns differ from Japan’s and the 
Philippines’. In contrast, the U.S., Japan, and the Philippines share a singular, urgent 
concern: Chinese expansionism in the Western Pacific – and specifically, Beijing’s attempts to 
control the waters around the Philippines, Taiwan, and Japan. All three are treaty allies among 
themselves (the U.S. being the hub connecting the spokes), which the Quad notably is not. As such, 
the level of military interoperability and trust is higher in the triangle. The U.S. and Japan 
have exercised and planned together for decades; the U.S. and Philippines have a mutual defense 
treaty and a history of joint operations; Japan and the Philippines are rapidly 
catching up with drills and agreements. This creates a more solid foundation to 
actually undertake joint deterrence activities, versus the Quad which remains a diplomatic 
coordination mechanism with each country acting largely in parallel rather than jointly.
Furthermore, minilaterals like this triad can be nimble. With just three countries, 
scheduling meetings, sharing intelligence, and making decisions can happen more quickly 
than in larger groups. There’s also a clarity of purpose: contain Chinese maritime aggression 
in East and Southeast Asia. Other partnerships often juggle multiple goals. ASEAN prioritizes 
economic integration and consensus diplomacy; the Quad invests in public goods like vaccine 
distribution and emerging tech governance, alongside security. The Iron Triangle has one big 
mission – uphold the regional status quo against unilateral Chinese changes – and each member 
brings complementary strengths to that mission. The Philippines contributes crucial geography 
and legitimacy (as the aggrieved coastal state enforcing its maritime rights); Japan contributes 
significant naval/coast guard capabilities and regional influence as Asia’s richest democracy; 
and the United States contributes superpower muscle and a global alliance network. Together, 
they form a tight “latticework of alliances and partnerships” that U.S. strategists see 
as essential to check China. In fact, U.S. policy in recent years has been to encourage 
such latticework – stitching bilateral ties into trilateral and quadrilateral formats. We see this 
not only with the U.S.-Japan-Philippines triad, but also the U.S.-Japan-South Korea trio (enhanced 
to address North Korean and Chinese threats in Northeast Asia) and the AUKUS partnership (U.S., 
UK, Australia) focusing on military tech in the Indo-Pacific. Each minilateral addresses a piece 
of the puzzle with fewer bureaucratic hurdles than, say, trying to get a formal NATO-like 
alliance of a dozen Indo-Pacific nations. Of course, none of this is to discount the 
importance of broader groupings. ASEAN will remain central to regional diplomacy, and its inclusive 
approach keeps China engaged in dialogue. The Quad provides a platform for the region’s major 
democracies (including India) to synchronize broader strategy and economics. But when it comes 
to on-the-water deterrence in the South China Sea, this slim trilateral has an edge. It is 
action-oriented. We have already seen it conduct joint coast guard drills, coordinate quadrilateral 
naval activities with Australia, and issue unified warnings to Beijing after incidents. None of those 
things happened through ASEAN or the Quad. In a way, the Iron Triangle acts as a force multiplier 
for the existing alliance system – it “networks” America’s separate alliances with Japan and the 
Philippines into a more effective combined front. The Biden administration explicitly 
pursued this: at the April 2024 summit, the joint vision statement from the three leaders 
spoke of building “a stronger networked security architecture” for the Indo-Pacific. Rather 
than rely solely on large, sometimes unwieldy coalitions, the idea is to form focused networks 
of allies who can address specific challenges. The U.S.-Japan-Philippines partnership is exactly that 
for the challenge of Chinese maritime coercion. In sum, while ASEAN struggles for consensus and 
the Quad moves deliberately, the nascent Iron Triangle can respond to events in near-real 
time. ASEAN might release a soft statement of concern on a South China Sea incident; 
the triad can jointly sail a coast guard cutter through the area that same week. The 
Quad might discuss infrastructure investment; the triad can plan out coordinated radar coverage 
or joint air patrols. There’s a certain liberating efficiency in having “the right players at 
the table” and no one else. To be clear, this alliance is not about supplanting ASEAN or 
the Quad – it’s complementary. The Philippines still works within ASEAN and values Southeast 
Asian solidarity; Japan and the U.S. still engage the region multilaterally. But when 
push comes to shove at a contested shoal, a smaller coalition of committed allies may be 
the only workable option to enforce international law (like the 2016 arbitral ruling) on the 
water. In the long run, if this Iron Triangle proves effective, it could even inspire similar 
minilateral approaches – perhaps nudging other partners (like Australia or Vietnam) to plug into 
flexible coalitions to uphold the rules at sea.

This is the New “Iron Triangle” Containing China in the South China Sea.

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