China's maritime assertiveness strains regional ties

Global Watch | 2026-04-30

China's maritime posture in East Asia is becoming more concentrated, more coercive and more strategically consequential.

In the South China Sea, coast guard and militia activity around Philippine-held approaches intensified through 2025. In the Taiwan Strait, Beijing ended the year with its largest blockade-style drills to date.

Neither front has produced a formal rupture in the regional order. But together they are making that order harder to sustain.

That matters because the waters linking the South China Sea, the Luzon Strait and the Taiwan Strait carry a substantial share of global seaborne trade and critical energy flows.

Disruption does not have to be total to be damaging. Repeated coercive incidents, uncertainty around offshore energy development and the steady normalization of Chinese patrols all raise geopolitical risk for shipping, investment and supply chains.

Washington and Manila said in their February 2026 strategic dialogue that they support "freedom of navigation and overflight" and "unimpeded lawful commerce" -- language that underscores how central open sea lanes remain to the wider regional economy.

Maritime pressure builds

The clearest shift has been in the South China Sea. The Asia Maritime Transparency Initiative (AMTI) found that China Coast Guard ship days at Scarborough Shoal more than doubled in 2025, while patrols near Sabina Shoal nearly tripled.

AMTI's own headline said Chinese patrols now "prioritize Scarborough" -- a useful shorthand for a broader pattern in which Beijing is concentrating pressure at flashpoints involving the Philippines.

Scarborough and Sabina are not isolated irritants. They sit within a wider contest over access, presence and precedent, a pattern echoed by China's covert campaign to destabilize the Philippines, which argues that maritime confrontations are being used to create a de facto reality that erodes international norms.

Resource competition sharpens that pressure further. AMTI has also tracked Chinese interference around Southeast Asian oil and gas activity, including near Malaysian and Vietnamese projects.

That reinforces a point already running through this picture: coercion at sea is not only about flags and patrol routes. It is also about who can explore, extract and insure commercially valuable activity in contested waters.

Regional governments have responded by tightening coordination rather than escalating recklessly.

Japan and the Philippines signed new security arrangements in January 2026 to deepen logistical and defense cooperation, underscoring a shared view that maritime coercion cannot simply be absorbed.

Washington has backed that effort through joint exercises, patrol cooperation and freedom-of-navigation operations aimed at keeping sea lanes open and maritime rights intact under international law.

Stability under strain

The Taiwan Strait reflects the same logic at a higher level of risk. Reuters reported that China's late-December "Justice Mission 2025" drills were its most extensive yet, spanning multiple zones and rehearsing the ability to encircle and pressure Taiwan.

Carnegie analysts have argued that gray-zone coercion is more likely than a near-term invasion, which helps explain Beijing's preference for cumulative pressure that stays just below the threshold of outright war.

The aim is not only military signaling. It is to test allied endurance over time.

That is why Washington's response has remained firm but measured. Its policy still emphasizes deterrence without a formal change to the status quo, even as support for Taipei and maritime coordination with Japan, Australia and the Philippines has expanded.

U.S. State Department briefings stress "peace and stability across the Taiwan Strait," while regional partners cast new defense ties as support for commerce, sovereign rights and open navigation.

The region is not on the brink of war. It is entering a period of tighter, more persistent friction across the first island chain.

For Washington and its partners, the challenge is not to answer each incident in isolation. It is to preserve open sea lanes, credible deterrence and enough diplomatic space to prevent miscalculation.

Reduce engagement, and the region becomes more dependent on Beijing's restraint. Sustain it, and there remains a stronger chance of keeping one of the world's most important maritime corridors open, predictable and secure.