Having spent years observing geopolitics in East Asia and in particular maritime security, over time one truth has become increasingly clear: the South China Sea is not just a contested maritime space. It is the stage for a slow-moving crisis — one that is inseparably linked to Beijing’s long-held ambition to annex Taiwan. As China escalates tensions in the region, it’s hard not to conclude that it is laying the groundwork for eventual military action against the island it sees as a breakaway province.

China’s pressure campaign is multi-dimensional — legal, economic, and increasingly military. Over the past year, these dimensions have converged at an alarming pace. What we are seeing is not a random display of naval might, but a deliberate strategy of coercion — designed to unsettle regional actors, fracture international resolve, and normalise Chinese military presence near Taiwan and across the wider South China Sea region.

The South China Sea is among the world’s busiest waterways, with roughly one-third of global shipping passing through it. Trillions of dollars in trade traverse this route annually. It is also rich in fisheries and suspected to hold substantial oil and gas reserves.

China, however, claims almost the entirety of the sea — a claim rooted in the so-called "nine-dash line", which was rejected by the Permanent Court of Arbitration in The Hague in 2016. That ruling, based on the United Nations Convention on the Law of the Sea (UNCLOS), found no legal basis for China’s expansive claims. Beijing, unsurprisingly, dismissed the verdict outright.

In the years since, China has militarised artificial islands in the Spratly archipelago, installing radar systems, anti-aircraft weapons, and runways capable of accommodating fighter jets and long-range bombers. It has frequently harassed Vietnamese and Philippine vessels, shadowed American warships conducting freedom of navigation operations, and rammed civilian boats.

In April 2024, the Philippines lodged a strong diplomatic protest after Chinese coast guard ships used water cannons and lasers against Philippine vessels near an atoll within Manila’s exclusive economic zone.

Similar incidents have multiplied in recent months.

More recently the Philippine military released footage showing Chinese ships blocking a resupply mission to troops stationed on a rusting warship beached intentionally on a reef. It was an act of brinkmanship — not dissimilar to China’s tactics near Taiwan that now occur on a daily basis.

And here is where the connection lies.

While the world is fixated on daily provocations in the South China Sea, a more dangerous shadow looms over Taiwan. In May 2024, after US-leaning President Lai Ching-te’s inauguration, Beijing launched large-scale military drills encircling the island, simulating a blockade in what was seen as a penalty of sorts for the Democratic Progressive Party (DPP) President Lai’s refusal to accept the “One China” principle. The message was unmistakable: this was rehearsed coercion, not just political theatre.

In the year since Lai’s inauguration, what has become increasingly evident is that China’s actions in the South China Sea are rehearsals for a Taiwan contingency.

Surveys carried out in Taiwan routinely show a populace largely under the belief that Taiwan will not invade any time soon despite claims by senior US officials in recent years that an attack on the island could take place by 2027.

The period of conscription in Taiwan was extended to 12 months from the previous four in late 2022 by Lai’s predecessor, President Tsai Ing-wen, but is yet to include women over the age of 18; something of a contradiction to Taiwan being lauded by the 2023 Social Institutions and Gender Index under the Paris-based Organisation for Economic Co-operation and Development which in first including Taiwan on the index, ranked the country “sixth worldwide and first in Asia among 179 countries and territories” according to Taiwan Today.

Meanwhile, the People's Liberation Army Navy (PLAN) has tested its ability to operate far from home ports, resupply at sea, and coordinate multi-branch operations. Beijing’s coast guard, nominally a civilian agency, has morphed into a grey-zone force equipped with naval-grade hardware.

It is being used to blur the line between law enforcement and military aggression — a tactic China is likely to replicate in a staged Taiwan scenario.

The linkage between the two theatres — South China Sea and Taiwan — is strategic. China is seeking to isolate Taiwan diplomatically while reshaping the surrounding maritime environment to its favour.

The goal is to make any potential intervention by the US or its allies in defence of Taiwan vastly more difficult. Control of the South China Sea offers Beijing a strategic buffer and a launchpad — it can disrupt logistics, impose blockades, and complicate any Western-led coalition’s access to the theatre.

That both Japan and South Korea host tens of thousands of US troops to the north of the South China Sea would immediately raise tensions should Beijing invade Taiwan, and while Taipei has been trying to increase the depth of its relations with Japan in particular in recent years, it remains unknown just how Tokyo would react to Chinese aggression against Taiwan.

Another aspect of China’s ongoing efforts to break down the island of 23mn are the cyber and informational dimensions of Beijing’s approach.

Taiwanese officials reported an increase in cyberattacks on government and infrastructure networks during and after the May 2024 drills. At the same time, Chinese state media amplified disinformation campaigns designed to sow doubt within Taiwan about US security commitments. Meanwhile, Beijing continues to court Pacific Island nations and ASEAN members with economic incentives, while punishing those who push back in an old-fashioned carrot and stick methodology, albeit one with sharp elbows.

Southeast Asian states, long wary of antagonising China, are now speaking more openly about the threat, however. Vietnam continues to bolster its maritime militia and develop deeper ties with the US and India despite in many ways being more ideologically related to China.

The Philippines has welcomed increased US troop rotations and joint patrols and Japan, while stifled for now by its pacifist constitution that some in Tokyo’s ruling Liberal Democratic Party are looking to amend, has pledged to double its defence budget. Even Australia has warned of the region’s “precarious” security environment.

But words and incremental defence enhancements are not enough. The West — particularly the US, UK, and EU — must do more to support regional deterrence in defending Taiwan.

That means more freedom of navigation patrols, a stronger and unified message in international forums, and greater military and economic assistance to vulnerable partners. The recent trilateral summit between the US, Japan, and the Philippines was a welcome start, but bigger and more frequent regional follow-through are essential.

War in the Taiwan Strait would be catastrophic — not just for Taiwan, but for global trade, regional security, and the international legal order. As such, the aim must be deterrence, not provocation of China.

But to deter effectively, Beijing’s constant efforts at destabilisation around Taiwan and across the South China Sea must be recognised. Incidents involving Chinese vessels in the area are not isolated incidents, but components of a long-term campaign.

And even as Taiwan is described as potentially the most dangerous flashpoint in Asia. I would go further: it is the fulcrum upon which the future of the Indo-Pacific — and by extension the global balance of power — may pivot.

If the West fails to respond decisively to China’s creeping aggression in the South China Sea, it may soon find itself unprepared for a far greater test.