ANALYSIS: Japan-Philippines vs China — Maritime Zone Delimitation Opens a New Pacific Front

ANALYSIS: Japan-Philippines vs China — Maritime Zone Delimitation Opens a New Pacific Front

Introduction: When two U.S. allies draw lines that Beijing refuses to recognize

May 28, 2026: the announcement that set everything in motion

On May 28, 2026, Philippine President Ferdinand Marcos Jr. and Japanese Prime Minister Sanae Takaichi announced together that they would open formal bilateral negotiations to delimit the maritime boundary of their respective exclusive economic zones (EEZs) and continental shelves — in the waters east of Taiwan. Beijing's reaction was immediate, blunt, and threatening: a spokesperson for China's Ministry of Foreign Affairs declared on June 2 that these negotiations were "completely illegal and null and void." China's Ministry of National Defense promised "resolute and firm actions" to defend Chinese territorial sovereignty and maritime rights.

What appeared to be a routine diplomatic procedure — two neighboring states delimiting their sovereign waters under the United Nations Convention on the Law of the Sea (UNCLOS) — became within days a major new flashpoint in the western Pacific. The reason: the area in question overlaps what China claims as its own EEZ and continental shelf east of Taiwan — territory that Beijing considers Chinese and over which it intends to exercise full sovereignty, without third-party involvement.

Three countries, one sea, zero arbitration in sight

The situation has a particular structural complexity: the EEZ claims of Japan and the Philippines overlap each other in certain areas, but they also overlap the claims of China and, more delicately, those of Taiwan. Taiwan's Ministry of Foreign Affairs responded on June 18, 2026 by requesting guarantees that the Japan-Philippines negotiations would not impinge on its own sovereign rights in the region, and by emphasizing that Taiwan is a distinct entity from mainland China — and that Beijing therefore has no right to speak on its behalf in this matter.

The result is a stack of overlapping claims in which four entities (Japan, the Philippines, China, Taiwan) have interests to assert, with no multilateral arbitration mechanism that all would accept. China has rejected the jurisdiction of the International Tribunal for the Law of the Sea (ITLOS) and the Permanent Court of Arbitration in similar cases. The 2016 precedent — in which the tribunal ruled against China on its South China Sea claims — remains the wound that Beijing refuses to reopen.

China's military response: patrols, research vessels, and "coastal governance"

The coast guard and People's Navy as instruments of the fait accompli policy

Beijing's reaction to the Japan-Philippines negotiations was not only verbal. From June 1, 2026, vessels of the Chinese Coast Guard (CCG) began continuous patrols in the waters east of Taiwan. From June 6 to 10, China's Ministry of Transport conducted a "special maritime law enforcement operation" in that same area — an action Beijing explicitly framed as a direct response to the Japan-Philippines talks.

Between June 16 and 18, the research vessel Xiang Yang Hong 22, belonging to the East China Sea Bureau of the Ministry of Natural Resources, conducted a "marine environmental survey" east of Taiwan. According to maritime tracking data from Starboard Maritime Intelligence, Chinese coast guard vessels patrolled east of Taiwan almost continuously from June 1 onward. The boundary between civilian scientific activity and military sovereignty projection is deliberately blurred.

The "coastal governance" model: extending the space of legal control

A Chinese social media account, Yuyuan Tantian, affiliated with state broadcaster CCTV, claimed on June 20 that Chinese activities east of Taiwan represent a new model of "coastal governance" — a regularized extension of law enforcement and research operations into waters that Beijing considers its "coastal waters." This same account had popularized the concept of the "Kinmen model" in 2024, referring to continuous coast guard deployments around Taiwan-administered Kinmen Island.

Extending that model east of Taiwan is strategically significant: it would allow China to free up People's Liberation Army Navy (PLAN) assets for longer-range missions in the Pacific, with the CCG covering the Taiwan Strait eastern approaches. Analysts at the AEI note that in Chinese blockade scenarios of Taiwan rehearsed during major exercises, the CCG is responsible for the Taiwan Strait while the PLAN covers the eastern approaches. The regularization of patrols to the east aligns precisely with this division of responsibilities.

Scarborough Shoal: the full-scale test of Chinese ambition

The floating platform: a test of international reaction

Alongside the tensions over the Japan-Philippines EEZs, the South China Sea saw another significant episode in June 2026. Satellite images from May 2026 revealed the presence of a floating platform of more than 27 square meters, equipped with an antenna and occupied by Chinese nationals, within the enclosure of Scarborough Shoal (Huangyan Dao in Chinese, Bajo de Masinloc in Filipino). Manila protested and demanded the structure's removal.

On June 17, 2026, the platform was withdrawn. But a research vessel from the Chinese Academy of Sciences (Tong Ji) was observed sailing toward the Shoal immediately afterward. China's response was to characterize the installation as a "temporary coral research facility" — a framing that Philippine and international observers found unconvincing, given the history of Chinese operations in the region.

The nature reserve paradox

In September 2025, China had officially designated the Huangyan Dao National Nature Reserve around Scarborough Shoal — a move that provides additional legal cover for justifying a permanent presence and potentially constructing facilities on the reef. This pattern mirrors exactly what was used for the artificial islands built in the Spratlys from 2013 onward: establishing facts on the ground, weathering international resistance, then gradual militarization.

Analysis by the Asia Times on June 27, 2026 described Beijing's strategy as "salami-slicing" — incremental actions that individually do not trigger a significant response, but that cumulatively reshape the status quo. Philippine Defense Secretary Gilberto Teodoro warned that if the platform was a precursor to a more permanent presence, Washington considers any physical construction at Scarborough Shoal a diplomatic red line.

Military exercises: the coalition building against Beijing

Valiant Shield and Resolute Dragon: unprecedented JSDF integration

In late June 2026, the United States and Japan were simultaneously conducting two major military exercises: Valiant Shield (June 11 to July 1) and Resolute Dragon (June 20 to 30). The most remarkable aspect of these exercises is the level of integration of the Japan Self-Defense Forces (JSDF): according to the U.S. Department of Defense, this is the second time that the JSDF have been "heavily integrated into the planning and execution" of Valiant Shield.

Valiant Shield also includes Australia, Canada, and New Zealand. Typhon missiles and HIMARS systems are deployed at Kanoya and on Amami Oshima island — and crucially, the Typhon systems will remain in Japan after the exercises conclude, a decision that significantly increases long-range strike capability in the Japanese theater.

Salaknib 2026: the largest coalition demonstration in Philippine history

The end of June 23, 2026 coincided with the closing of Salaknib 2026, the largest joint military exercise in Philippine history, involving more than 7,000 soldiers from the Philippines, the United States, Japan, New Zealand, and Australia. The same day, a rare confrontation occurred: four Chinese warships challenged the Philippine frigate BRP Diego Silang near Scarborough Shoal, with radio exchanges demanding that each vessel leave the area.

This confrontation — occurring on the very day a multinational exercise involving 7,000 soldiers concluded — illustrates the escalation-deterrence dynamic at work in this region. Allies are building shared capabilities. China is testing limits in parallel. Neither side wants to provoke an armed incident at this stage — but the margin for error is narrowing.

The geopolitics of the EEZ: why this maritime dispute matters for world order

UNCLOS and the Chinese challenge to the international maritime order

At the heart of this conflict lies a fundamental question for international order: do the rules of the United Nations Convention on the Law of the Sea (UNCLOS) apply to China? UNCLOS grants coastal states a 200-nautical-mile EEZ over which they exercise sovereign rights over resources. It also provides mechanisms for delimiting overlapping zones. The procedure that Japan and the Philippines have initiated is a standard application of UNCLOS.

China is a signatory to UNCLOS, but applies it selectively — invoking its provisions when they serve Chinese interests, rejecting them when they constrain. Its ten-dash line, which claims nearly the entire South China Sea, has no basis in UNCLOS and was explicitly invalidated by the Permanent Court of Arbitration in 2016. That Beijing continues to use it as the foundation for its territorial claims is a deliberate and systematic violation of international maritime law.

Implications for Taiwan and regional security

The extension of Chinese coast guard operations east of Taiwan has implications that reach beyond the Japan-Philippines EEZ dispute. By regularizing its presence in these waters, China is seeking to normalize its jurisdiction around Taiwan in a manner similar to what it has done around Kinmen: a permanent presence that gradually erodes Taiwan's effective sovereignty over its own coastal waters.

For the United States, whose Taiwan policy rests on maintaining the status quo — neither formal independence for Taiwan nor forced reunification — this Chinese normalization of maritime presence is deeply destabilizing. It forces Washington either to respond to each new transgression (politically difficult to sustain) or to let the status quo deteriorate gradually (dangerous for the credibility of American deterrence). That is precisely the dilemma that China's "salami-slicing" strategy is designed to create.

The coalition of democracies: fragile but growing

Reciprocal access agreements: weaving the network of deterrence

The democratic response to Chinese maritime pressure is taking the form of a gradually expanding network of bilateral and multilateral agreements. Japan and the Philippines signed a reciprocal access agreement allowing their armed forces to train and conduct exercises on each other's territory — a remarkable development for a country like Japan, whose constitutional constraints on external military projection long limited this type of cooperation.

Philippine Defense Secretary Teodoro raised the possibility of a rotational presence of Philippine forces in Japan and vice versa — a symmetry that would have been unthinkable a decade ago. The Philippines have also signed access agreements with Australia, New Zealand, Canada, and France. This gradual interlocking creates a regional security architecture that, while less formal than NATO, offers non-trivial deterrence.

The limits: an architecture without a mutual defense treaty

Despite this progress, the Pacific anti-China coalition suffers from a fundamental limitation: there is no equivalent of the North Atlantic Treaty that would automatically obligate members to defend each other in the event of an attack. The Philippine-American Mutual Defense Treaty is the cornerstone of regional security, but its activation in the event of a Chinese attack on Philippine vessels in the South China Sea is subject to ongoing debate about its precise interpretation.

The AUKUS alliance (Australia, United Kingdom, United States) and the Quad (United States, Japan, Australia, India) are important advances, but they do not create automatic mutual defense obligations. In this vacuum, China can continue to play on ambiguities — until an incident spirals out of control, or until the democracies build a more robust architecture.

The maritime economy at stake: fisheries, hydrocarbons, and undersea cables

Fisheries: a livelihood for millions of fishermen

The contested waters between Japan, the Philippines, and China are not only strategically significant in the military sense — they are economically vital for millions of artisanal fishermen across the region. The South China Sea accounts for roughly 10% of global fish catch and provides a source of protein and income for coastal communities in the Philippines, Vietnam, Indonesia, and China. The permanent presence of Chinese coast guard vessels around Scarborough Shoal and in other disputed areas has drastically reduced Filipino fishermen's access to traditional fishing grounds located within their own EEZ.

Reports from the Philippine marine human rights organization Pamalakaya document regular harassment of Filipino fishermen by Chinese coast guard: water cannons used to disperse boats, equipment seizures, blockades of access routes to fishing zones. These incidents — increasing in frequency since 2023 — have a direct and concrete impact on the livelihoods of some of the most vulnerable communities in the Philippines. The maritime dispute is not abstract to these fishermen: it translates into reduced catches and declining incomes.

Hydrocarbons and digital cables: the other strategic stakes

Beneath the contested waters of the South China Sea lie potential hydrocarbon reserves estimated at tens of billions of barrels of oil equivalent, although estimates vary widely and exploitation remains technically complex and economically uncertain at current price levels. China has nevertheless signaled clearly its intention to control these potential resources by constructing artificial islands in the Spratly archipelagos and deploying oil exploration equipment in disputed areas.

Less visible but equally strategic: the South China Sea hosts a dense network of submarine telecommunications cables carrying a significant portion of internet traffic between Asia, Europe, and North America. Effective control over these waters would give a hostile actor the capacity to monitor, intercept, or cut these cables — a digital infrastructure weapon with enormous economic and security consequences. Western intelligence services have documented suspicious Chinese activity near several of these strategic cables.

Taiwan as the central geostrategic variable in the EEZ conflict

Taipei's reaction: neither Beijing's proxy nor abandoning sovereign rights

Taiwan's position in this maritime dispute is particularly delicate. On one side, Taiwan's Ministry of Foreign Affairs clearly rejected any pretension by Beijing to speak on its behalf in the Japan-Philippines negotiations, emphasizing on June 18, 2026 that Taiwan is a distinct entity from mainland China with its own sovereign rights in the region. On the other side, Taipei itself claims a portion of the waters east of Taiwan based on its own interpretation of maritime law — claims that partially overlap with those of Tokyo and Manila.

This complex position of Taiwan — adversary of Chinese pretensions but holder of its own claims — illustrates the difficulty of building a united front among democracies against China in this region. The Japan-Philippines negotiations will at some point need to coordinate with Taipei, or risk creating frictions with a partner whose support is strategically crucial in any scenario of resistance to Chinese expansionism.

A conflict around Taiwan and its implications for disputed EEZs

In any scenario of military conflict around Taiwan — whether a blockade, an invasion, or American intervention — the disputed waters east of Taiwan would immediately become a critical operational theater. Rights of passage, exclusion zones, coast guard patrols — all the questions that Japan-Philippines negotiations are attempting to resolve in peacetime would take on immediate military dimensions in a crisis. This is why the normalization of Chinese presence in these waters — through coast guard patrols and "coastal governance operations" — is strategically significant: it prepares the legal and operational ground for crisis scenarios.

Analysts at the AEI in their report of June 26, 2026 note that the China Coast Guard's capacity to sustain continuous patrols east of Taiwan frees up People's Liberation Army Navy assets for more offensive missions in other sectors. This division of responsibilities — the CCG for normalizing presence in contested zones, the PLAN for long-range operations — is consistent with operational preparation for a crisis scenario around Taiwan.

Conclusion: a maritime boundary, a test for world order

What China is seeking to establish as the norm

Beijing's response to the Japan-Philippines negotiations reveals a clear ambition: that China must be associated with any negotiation over waters it claims, even when those waters are internationally recognized as falling under the sovereignty of other states. If this norm becomes established — if the world tacitly accepts that China holds a veto over the maritime arrangements of its neighbors — the entire framework of international maritime law in the region becomes moot.

This is not merely a question of fish or mineral resources. It is a question about the type of international order that will prevail in the twenty-first century: an order based on negotiated rules respected by all, or an order based on power in which the strongest dictate terms to the weakest. China has chosen its side. The question is whether the West is prepared to defend its own.

What the West must do

The European Union, the United Kingdom, and other democracies must engage more actively in Indo-Pacific maritime security — not to seek confrontation with China, but to demonstrate that international rules have defenders beyond just the directly affected countries. European naval deployments in the region — already undertaken by France, Germany, and the United Kingdom — must become more regular and more coordinated.

Solidarity with Japan and the Philippines in their right to delimit their EEZs in accordance with international law is a matter of principle that concerns all democracies. If we allow China to decide who has the right to talk to whom about the planet's waters, we will have accepted the terms of a world in which the rule of the strongest replaces the rule of law. That is not the world order the West helped build since 1945.

By Maxime Marquette, columnist

Columnist's transparency note

Method and sources

Maxime Marquette is a columnist and analyst specializing in Indo-Pacific geopolitics and strategic affairs. This analysis is based on public sources: the AEI weekly report of June 26, 2026, dispatches from Xinhua, the South China Morning Post, the Japan Times, the Asia Times, the Financial Times, and other regional media. No confidential government sources were consulted.

Maritime tracking data (vessel positions, trajectories) are based on open-source commercial data (Starboard Maritime Intelligence) and not on classified intelligence. Strategic analyses of Beijing's intentions are analytical interpretations based on observable behavior, not certainties.

Position and bias

The columnist considers Chinese territorial claims in the South China Sea and East China Sea to be largely unsupported in international law and potentially destabilizing to regional order. This position is consistent with this publication's editorial doctrine. The Chinese perspective — presented in the article through China's own official statements — is reported faithfully without being endorsed.

Sources

Primary sources

AEI — China & Taiwan Update, June 26, 2026 — June 26, 2026

Xinhua — Japan, Philippines slammed for delimitation talks — June 9, 2026

People's Daily — China slams Japan, Philippines over maritime delimitation — June 26, 2026

Secondary sources

South China Morning Post — China and Philippines in rare naval stand-off near Scarborough Shoal — June 23, 2026

Japan Times — Japan-Philippines maritime talks 'big step' — June 8, 2026

Asia Times — China tests Scarborough as Manila casts beyond US for help — June 27, 2026

MOFA Taiwan — Response to Japan-Philippines maritime boundary negotiations — June 18, 2026