CHATHAM HOUSE How Beijing might rule the South China Sea within a decade William Matthews and Ben Bland create a speculative ‘backcasting’ scenario: ‘It’s the year 2035 and China dominates the region’. They describe how that might come to pass – and how to avoid it. The World Today Published 15 September 2025 Updated 19 September 2025 —

CHATHAM  HOUSE 

How Beijing might rule the South China Sea within a decade

William Matthews and Ben Bland create a speculative ‘backcasting’ scenario: ‘It’s the year 2035 and China dominates the region’. They describe how that might come to pass – and how to avoid it.

The World Today

Published 15 September 2025

Updated 19 September 2025 —

9 minute READ

Image — A PLA Navy fleet takes part in a review in the South China Sea in 2018. Photo: Getty Images.

William Matthews

Senior Research Fellow, Asia-Pacific Programme

Ben Bland

Director, Asia-Pacific Programme

15 September, 2035: As the Zhejiang, an 80,000-ton nuclear-powered aircraft carrier, drifted into Manila’s port yesterday, the Chinese delegation was given a warm welcome by thousands of watching Filipinos. Officially, the visit was to mark the fifth summit of the China–Philippines Dialogue on Maritime and Climate Security. In effect, it represented the moment China achieved a decades-long ambition: control of the South China Sea.

Philippine recognition of China’s claims was unthinkable only 10 years ago.

On the flight deck of the Chinese navy’s most advanced ship, leaders of both countries announced a raft of new climate aid pledges by Beijing with a joint statement endorsing the Maritime Community of Shared Future for the South China Sea. The deepening ties between the two countries mark the Philippines’ official recognition of the waters within the 10-dash line as China’s sovereign territory, leaving Vietnam the sole Southeast Asian nation contesting Beijing’s claims in the South China Sea.

Philippine recognition of China’s claims was unthinkable only 10 years ago. That was before Washington’s unilateral decision to tear up its defence pact with Manila – part of an attempt to curry favour with isolationist voters in the run-up to the 2030 mid-terms. That put to rest any lingering hope of serious US opposition to China’s increasingly aggressive intimidation of Philippine vessels in the region.

The Spratly Incident

Earlier in 2030, intimidation resulted in the sinking of a Philippine fishing vessel and the death of several crew members in a ramming incident with a Chinese People’s Maritime Militia unmanned patrol vessel. China denied any involvement. The diplomatic silence across Southeast Asia was palpable. Few external powers now challenge China’s position in the South China Sea. The routine joint exercises that the United States, Japan, France, Britain, Australia and others often held alongside regional partners are now distant memories.

No non-Chinese military vessel has crossed the 10-dash line, which demarcates the area of sea over which China claims sovereignty since the Spratly Incident in 2031. Following the joint recognition of China’s territorial claims by Brunei, Indonesia, Malaysia and Thailand at the inaugural summit for the Maritime Community of Shared Future for the South China Sea in 2029, Beijing’s rhetoric on the South China Sea changed. Increasingly, it made reference to ‘grave and devastating’ consequences for any foreign power ‘seeking to undermine the eternal historical truth of China’s inalienable sovereignty over the South China Sea’.

In 2031, the Australian government quietly sought to test China’s resolve amid the winding down of US commitments in the region, Japan’s increased focus on its own disputes with China in the East China Sea and the inability of European countries to maintain naval operations so far from home. An unmanned Royal Australian Navy Large Optionally Manned Surface Vessel, equipped with a US-made Aegis air-and-missile defence system, crossed the 10-dash line on a course towards the Spratly Islands. 

The 10-Dash Line: China’s disputed claim to the South China Sea

map of South China Sea

— This map is based on maps circulated by the Chinese government in 2009 and 2023. It is an approximate representation and not exactly to scale. The boundaries and names shown and designations used on the map do not imply endorsement or acceptance by the authors or Chatham House. Map boundaries from World Bank; the extent and location of Spratly Islands is an approximation based on a 2015 US State Department map.

The most authoritative accounts suggest that its presence triggered a swarming response from Chinese drones, which overwhelmed the vessel’s defences and sank it. China denied ordering such an attack. Australia acknowledged an accident involving one of its vessels and launched an inquiry into the cause, results of which have never been made public. The incident would become the first and last attempt by any power to deploy a naval vessel across the 10-dash line since China completed the rollout of its Zheng He vessel identification system.

Topics

China’s foreign relations

Regions

Southeast Asia China

Departments

Asia-Pacific Programme

The road to 2035

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