Interviews | Security | Southeast Asia

The South China Sea and the Philippines’ Defense Strategies 

Insights from Su Mon and Tomas Buenaventura.

A photo released by the Armed Forces of the Philippines that claims to show a China Coast Guard vessel firing a water cannon in the vicinity of Second Thomas Shoal in the South China Sea, Aug. 20, 2025.

The Diplomat author Mercy Kuo regularly engages subject-matter experts, policy practitioners, and strategic thinkers across the globe for their diverse insights into U.S. Asia policy. This conversation with Su Mon and Tomas Buenaventura – Asia Pacific senior analyst and senior research assistant, respectively, at ACLED (Armed Conflict Location and Event Data) – is the 523rd in “The Trans-Pacific View Insight Series.”

Examine the South China Sea conflict escalation environment based on ACLED data.

ACLED data reveals the South China Sea security environment is increasingly defined by the normalization of gray zone tactics and rapid militarization. A persistent state of confrontation significantly escalated in the first half of 2026, with a roughly 490 percent increase in Chinese force movements between January and June compared to the previous six months. This activity is concentrated within the Philippines’ Exclusive Economic Zone (EEZ), specifically around Scarborough Shoal, Sabina Shoal, and Thitu Island.

This uptick in force movements — including survey vessels, China Coast Guard (CCG) deployments, and maritime militia — is often accompanied by more frequent encounters, ranging from harassment and blocking maneuvers to competing law enforcement operations. These activities are not just about presence, but about altering the status quo on the seas. They represent a coordinated effort to advance territorial claims and consolidate control, keeping tensions high while strategically averting open military conflict. 

Essentially, the region has become a primary theater for power projection, where the margin for error is shrinking, and the risks of a miscalculation that could lead to broader instability are becoming more acute.

How are gray zone tactics affecting the chance of escalation in the South China Sea?

The real danger with gray zone operations is not necessarily that they will spark an immediate war; it’s that they gradually normalize coercion. By using persistent, incremental actions — such as the routine deployment of maritime militia and coast guard vessels — Beijing is steadily shifting the status quo, redefining “normal” maritime activity in a way that feels manageable daily but creates significant long-term strategic shifts.

ACLED’s South China Sea Monitor suggests that these gray zone operations are expanding into cyber warfare, intelligence operations, and suspected sabotage against critical infrastructure. This expansion shows the growing imbalance between China and other claimant states, necessitating stronger cooperation among regional partners and allies to respond effectively.

Ultimately, this creates a dangerous environment where the primary risk is not a deliberate decision to go to war, but a miscalculation. As these tactics become more sophisticated, they blur strategic intent and erode the trust needed to manage crises. Regional security and coordination mechanisms, such as the South China Sea Code of Conduct negotiations, have not kept pace with these developments, leaving a widening gap in governance, making the region increasingly vulnerable to unintended escalations.

Identify key developments in the Scarborough Shoal and the Spratly Islands.

The situation at Scarborough Shoal has remained tense since China established de facto control there in 2012, despite the feature falling within the Philippines’ EEZ. Beijing has maintained a constant presence, with the CCG and maritime militia frequently blocking, ramming, and using water cannons against Philippine vessels. Tensions intensified after Beijing designated the shoal a national “nature reserve” in September 2025 — a move China framed as........

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