Flag Raised, Tensions Soar: China’s Bold Seizure of Sandy Cay Escalates South China Sea Confrontation

(DEFENCE SECURITY ASIA) — In a bold escalation of its assertiveness in the South China Sea, China’s coast guard forces have occupied another isolated reef, hoisting the national flag atop Sandy Cay, a feature alarmingly close to a Philippine military garrison.

Beijing formally declared sovereignty over Sandy Cay, underscoring a hardening stance in a maritime theater already fraught with escalating rivalries among claimants.

Photographs released by Chinese state media captured the moment coast guard personnel raised the red flag of China over Sandy Cay, which Beijing now officially refers to as Tiexian Jiao.

Located within the disputed Spratly Islands, Sandy Cay is situated in one of the world’s most contested maritime regions, claimed simultaneously by Taiwan, Vietnam, the Philippines, and China.

Positioned just three kilometers from Thitu Island — known locally as Pag-asa Island — Sandy Cay lies perilously close to a Philippine military installation hosting an airstrip, defensive structures, and a small civilian population of roughly 250 residents.

Citing the nationalist tabloid Global Times, Chinese officials claimed their coast guard landed on Sandy Cay to “conduct inspections and record illegal activities,” including clearing the reef of plastic waste, driftwood, and debris — an operation portrayed as benign environmental stewardship but viewed with deep suspicion by Manila.

Beijing asserted in January that its forces had “intercepted and repelled” Philippine Navy vessels it accused of “intruding” into the waters near Sandy Cay while allegedly attempting “an illegal landing and sand sample collection.”

The Philippines countered by stating that it had deployed its coast guard to monitor the area and study whether China was conducting preliminary activities for small-scale land reclamation — a tactic Beijing previously used as the first step in major militarization campaigns elsewhere in the Spratly chain.

China insists that Sandy Cay, spanning a modest 200 square meters, is a natural maritime feature rather than an artificial construction, granting it — under China’s interpretation of international law — a 12-nautical-mile (22-kilometer) territorial sea, dangerously overlapping waters around Thitu Island.

As of now, Manila has refrained from issuing an official diplomatic response to China’s occupation of Sandy Cay, reflecting the Philippines’ delicate balancing act between resisting Chinese assertiveness and avoiding escalation.

Nevertheless, Filipino maritime security officials and regional analysts have raised alarm, viewing Beijing’s formal claim over Sandy Cay as a prelude to increased harassment of Filipino outposts across the Spratly archipelago.

A senior Philippine maritime security official, speaking anonymously, warned that while China has yet to establish a permanent facility on Sandy Cay, its declaration of sovereignty could foreshadow “escalating interference against Philippine operations on Pag-asa Island.”

Over the past year, Philippine efforts to assert presence at Sandy Cay have been repeatedly frustrated, as Chinese coast guard vessels aggressively blocked access and issued stern warnings for Philippine ships to withdraw.

This latest flashpoint emerges as the Philippines and the United States conduct “Balikatan 2025,” the largest joint military exercise in their alliance’s history, incorporating coastal defense drills and amphibious island retaking operations that directly mirror real-world South China Sea contingencies.

China’s move to consolidate control over Sandy Cay is widely interpreted as a calculated test of Manila’s political will and Washington’s commitment under the 1951 Mutual Defense Treaty, at a time when U.S. security guarantees are under intense scrutiny globally.

While no official countermeasures have yet been announced by the Marcos administration, regional observers expect the Sandy Cay episode to sharpen diplomatic fault lines and further entrench the South China Sea as one of Asia’s most dangerous flashpoints.

Between 2013 and 2016, Beijing embarked on one of the most ambitious island-building campaigns in modern history, transforming seven submerged reefs across the Spratlys — including Fiery Cross Reef, Subi Reef, and Mischief Reef — into sprawling military outposts.

Through colossal dredging operations, China relocated hundreds of millions of cubic meters of sand and coral, constructing artificial islands outfitted with 3,000-meter runways, deep-water naval ports, hardened aircraft hangars, sophisticated radar arrays, and surface-to-air missile sites.

These installations effectively extended the range of China’s military power projection deep into Southeast Asia’s maritime heart, enabling persistent aerial, surface, and undersea surveillance of some of the world’s busiest commercial sea lanes.

The island fortifications also serve as launchpads for advanced systems such as HQ-9B long-range surface-to-air missiles and YJ-12 anti-ship cruise missiles, drastically altering the military balance by placing Philippine, Malaysian, Vietnamese, and even U.S. assets at heightened risk.

China’s strategy of physically reshaping the maritime domain has been accompanied by legal arguments invoking the so-called “Nine-Dash Line,” an expansive historical claim rejected by neighboring states and overwhelmingly invalidated by a landmark 2016 ruling by the Permanent Court of Arbitration in The Hague.

That tribunal ruled unequivocally that China’s sweeping claims had no legal basis under the United Nations Convention on the Law of the Sea (UNCLOS) and that Beijing’s reclamation activities had caused severe environmental destruction to fragile coral ecosystems.

Despite the international legal defeat, Beijing dismissed the tribunal’s authority and proceeded unabated with militarization efforts, signaling a willingness to bear global censure in exchange for irreversible gains on the ground.

Today, China’s militarized artificial islands function as fortified bastions, allowing the People’s Liberation Army Navy (PLAN) and Air Force (PLAAF) to monitor, challenge, and, if necessary, dominate maritime movements across critical chokepoints linking East Asia with the Middle East, Africa, and Europe.

The occupation of Sandy Cay — small in physical size but enormous in symbolic significance — marks the latest maneuver in Beijing’s broader strategy to assert “gray zone” control over the South China Sea, using non-military forces like the coast guard and maritime militia to advance strategic goals without triggering outright conflict.

In an era of mounting U.S.-China rivalry, where flashpoints from Taiwan to the South China Sea could ignite broader confrontations, every reef, every cay, and every decision carries potentially global consequences.

— DEFENCE SECURITY ASIA