When Manila and Tokyo draw a line, Beijing draws a red line

The clause that sets this off is a short one. At a summit in Tokyo in late May, Prime Minister Sanae Takaichi and President Ferdinand Marcos Jr agreed that Japan and the Philippines would open formal talks to delimit the boundary of their exclusive economic zones and continental shelves, in accordance with international law. Two neighbours proposing to draw a line between their waters is, on its face, an administrative matter.

Beijing refused to read it that way. Within a day, the foreign ministry declared the move completely illegal and void, on the grounds that the waters at issue, directly east of Taiwan, fall within China’s own economic zone and continental shelf. Rhetoric was followed by hulls. The China Coast Guard deployed vessels for what it called law-enforcement patrols east of Taiwan; through June, the pressure spread north, with Chinese ships operating inside Japan’s economic zone south of Yonaguni and escorting official vessels there, conduct that Tokyo’s Chief Cabinet Secretary, Minoru Kihara, called unacceptable.

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In early July, a state maritime affairs institute under the natural resources ministry branded the negotiations an internationally wrongful act and asserted China’s right to hold both governments to account. Taipei’s answer was much quieter, reflective of its diminished status in geopolitical events, but also assured. Rather than condemn the talks, it asked to be consulted, sought assurances that its fishing arrangements with both countries would remain in place, and told its offices in Manila and Tokyo to verify the details, before sending its own coastguard vessels to the area. Beijing, by contrast, tied the boundary to the One-China principle and demanded that the talks cease. Far from pushing the two sides of the Strait together, the episode widened the space between them.

A line that touches a third coast

The reason a modest delimitation provokes all this belongs to the map. Both countries are sprawling archipelagos. The zone projected from the Philippines’ northernmost islands, the Batanes, meets the one projected from Japan’s southernmost Ryukyus in the waters east of Taiwan, and China claims an economic zone and continental shelf there too, drawn from an island it regards as its own. The three sets of entitlements overlap almost everywhere. The sliver where only Japanese and Philippine waters meet, untouched by any Chinese claim, is slight.

Where such zones overlap, the law of the sea has neighbours settle them by agreement, which is exactly the mechanism Tokyo and Manila have invoked. The trouble is that almost any line worth agreeing runs through space Beijing insists is partly its own.

That is the bind. A bilateral Japan-Philippines boundary would, in effect, treat the sea around Taiwan as something to be shared out among the island’s neighbours rather than as an extension of Chinese sovereignty.

A line settled without China implies that Taiwan’s waters are not Beijing’s to allocate. No agreement between two states can bind a third in law, so the delimitation could not, by itself, take anything from China. But precedents accrete, and a settled line, drawn on a chart and defended by patrols, becomes the reference point for the next contest. Beijing’s demand that any such talks include China is an attempt to turn its claim over Taiwan into authority over the sea around it, and to make its consent the price of its neighbours acting at all.

Hence the hardening rhetoric from Beijing. Rallying allies to pressure China, a foreign ministry spokesman said, would not work — an effort to recast two sovereign states settling their own boundary as a hostile bloc.

The partnership Beijing is watching

The talks did not appear from nowhere. They crown a relationship that has thickened across every domain, and that breadth, more than the boundary, is what Beijing tracks. The Philippines was the first foreign buyer of finished Japanese defence equipment, taking air-surveillance radars delivered in 2023 and 2024 and five coastal radars this February, after Tokyo relaxed a post-war ban on arms exports. It was the first recipient of Japan’s Official Security Assistance. Under a reciprocal access agreement, ratified in September 2025, it became the first Asian state to let Japanese forces train on its soil. Japan has handed over the Philippines’ largest coastguard ships and lined up decommissioned destroyers for transfer.

The military side is only the visible edge. Japan is also underwriting the first Metro Manila Subway, helping fund a commuter railway through the former American airbase at Clark, and anchoring the Luzon Economic Corridor, a ports-and-rail scheme launched at a 2024 Marcos–Kishida–Biden summit in Washington and now tied to a US-led plan for an artificial intelligence hub.

The Philippines’ first free-trade agreement, in force since 2008, was also with Japan. Both are US allies at odds with China, and both have drifted from the old hub-and-spokes model towards the newer minilaterals, from the Quad to the “Squad”, which adds Australia and the Philippines.

In 2025 Japan’s then defence minister, Gen Nakatani, floated treating the East China Sea, the South China Sea and the Korean peninsula as one theatre; a settled sea corridor east of Taiwan would help knit those spaces together. That is what gives a technical map exercise its weight. It arrives at a time as Tokyo chooses rearmament over restraint, loosens its export rules, and as Washington, absorbed by its war with Iran, leaves Pacific partners guessing about its focus.

The clearest signal came in the spring. During the Balikatan exercises, roughly 1,400 Japanese personnel deployed to the Philippines, marking the first Japanese combat troops on Philippine soil since the Second World War. On 6 May, a Japanese launcher on Luzon’s north-west coast fired two Type 88 anti-ship missiles that sank a decommissioned warship about 75 kilometres offshore, Japan’s first firing of an offensive missile beyond its territory since 1945. A day earlier, American forces had launched a Tomahawk from the Typhon system across the archipelago. Read as a set, these are the components of a missile screen along the First Island Chain, hinged on the Luzon Strait, the channel a Chinese fleet must cross to reach the Pacific or move on Taiwan from the east.

The veto question

When we take the map out of the equation, the dispute reduces to a principle China has pressed for years: that its neighbours should clear their strategic choices with it first. The claim that the waters east of Taiwan are China’s to govern cannot be separated from the claim that Japan and the Philippines may not fix their own boundary without Chinese participation.

The sharper danger, as analysts in Manila have warned, is that the enforcement outlasts the diplomacy. Beijing has used the announcement as a licence to make its coastguard a fixture in waters where its presence was previously intermittent. After Nancy Pelosi’s 2022 visit to Taipei, China discarded the Strait’s informal median line, normalised military drills, ringed the island with exercise zones, two of which overlapped Japanese and Philippine waters, and dropped missiles into Japan’s economic zone. What began as a reaction became the new baseline. On that record, new facts at sea may settle the matter before the negotiators do, whatever line they eventually agree.

Manila is exposed, and with each new fact at sea in the region, its exposure increases. It is turning itself into a forward platform in a contest it lacks the weight to steer, hosting systems it neither owns nor can redeploy; South Korea, which watched American launchers move off its territory over its objections, is the cautionary case. The prudent reading is that the Philippines is spreading its bets precisely because it can no longer count on a single guarantor.

The principle, though, outsizes any one boundary. If a negotiation between two sovereign states can be halted by a third that declares it illegal and sends ships to prove the point, the veto holds. If the talks go forward, it does not. A small argument over where to draw a line has become the ground on which that far larger question is settled.

(Views expressed in the above piece are personal and solely those of the author. They do not necessarily reflect Firstpost’s views.)