Just west of Palawan in the heart of the South China Sea, the BRP Sierra Madre sits grounded atop a submerged reef, its sailors withering away with the rusting hull of a ship that has not sailed in almost three decades. Yet the sailors are not stranded, and the ship’s grounding was not an accident. The BRP Sierra Madre serves as a critical military outpost, intentionally placed and continuously manned to legitimize the Philippines’ territorial claims of portions of the Spratly Islands archipelago—a disputed collection of roughly one hundred low-lying land features and reefs that, prior to the twentieth-century, played virtually no role in shaping maritime activity in the South China Sea. Such extreme tactics represent just one end of a spectrum of actions being taken by the South China Sea’s coastal states in response to an increasingly multifaceted dispute that has grown to entangle military, economic, and strategic interests alike.

Despite the Spratly Islands’ relative insignificance in the past, various claimants—such as, but not limited to, the Republic of China (ROC), the People’s Republic of China (PRC), Vietnam, and the Philippines—once sought access to the archipelago for strategic naval purposes, especially in the lead-up to and immediate aftermath of World War II. The economic exploitation of the Spratly Islands’ rich natural resources is a relatively recent development, and evidence suggests that any sustained habitation or military activity on the archipelago’s larger islands has been rare. It was not until the 1970s that scientists began hinting towards the fact that the “Spratlys may lie atop an ‘elephant’ of petroleum, with potential to yield in excess of a billion barrels of oil and untold quantities of natural gas.” South Vietnam, the ROC, and the Philippines slowly amassed troops on the archipelago’s larger islands, but none leveraged their forces to seize greater territorial holdings. Shortly after, in 1982, the adoption of the United Nations Convention on the Law of the Sea (UNCLOS) introduced the concept of exclusive economic zones (EEZs). When UNCLOS entered into force in 1994, it marked the single most significant contribution to customary international law governing maritime behavior to date; yet, it also triggered a scramble to bolster Spratly Islands holdings. Under UNCLOS’ EEZ provisions, coastal states were afforded full sovereignty of the undersea and seabed resources extending up to two hundred nautical miles beyond their coastal shorelines—thereby adding a lucrative economic dimension to the Spratly Islands’ outstanding territorial disputes. The matter is further complicated by the fact that, due to the centrality of the archipelago in the South China Sea, many of the coastal states’ EEZ boundaries overlap through the Spratly Islands, leaving critical questions of sovereignty rights unanswered. By the 1990s, all four of the original claimants, in addition to Malaysia, established garrisons on portions of the archipelago to militarize their stakes. The PRC, ROC, and Vietnam claimed the entire archipelago outright, each attempting to maximize their shares of the metaphorical “elephant” in the absence of any supporting legal framework. Notably, the PRC’s EEZ fails to intersect the Spratly Islands at all.

Modern skirmishes among the Spratly Islands’ claimants, particularly between the Philippines and the PRC, can therefore be understood as an extension of a broader, decades-long strategic competition fueled by ambiguity. While these clashes often occur below the threshold of open violence, the PRC’s People’s Liberation Army Navy (PLAN) and China Coast Guard (CCG) have taken increasingly aggressive action against Philippine Navy and Coast Guard (PCG) vessels in recent years. This past June, two PCG vessels attempting to resupply watchstanders on the Sierra Madre with critical food and water stores were seized by the CCG. The Filipino sailors sustained minor injuries in a “scuffle” with CCG personnel on speedboats. Two more incidents occurred just months later in a series of collisions between CCG and PCG vessels—the first time that CCG and PCG vessels have directly engaged over Spratly Island territory. 

Despite international condemnation, the PRC contends that their operations in the Spratly Islands have been conducted with due regard to maritime safety, instead suggesting that the Philippines’ dangerous maneuvering and illegitimate territorial claims are to blame for escalating regional tensions. International arbitration of these disputes through the lens of UNCLOS has been historically futile, and the PRC—despite ratifying the treaty—continues to successfully undermine a rules-based maritime order in the archipelago. The United States, however, remains committed to stymieing these strategic victories. In a July visit to Manila, U.S. Secretary of State Antony Blinken announced the provision of roughly $500 million in aid to the Philippines’ fleet modernization efforts. More recently, the U.S. Naval Institute reported that the U.S. has pledged to assist the Philippines in constructing a new naval pier at Subic Bay—a westward-facing, South China Sea-adjacent, deepwater port capable of hosting larger naval vessels. The U.S. and the Philippines have long fostered a strategic military relationship, but each of these developments points toward a coordinated response to this past summer’s skirmishes.

The regional ramifications of deteriorating Sino-Philippine relations are now even clearer. Naval confrontations in the Spratly Islands, no matter how small, have already driven merchant mariners to bottleneck along “a small number of increasingly busy routes,” so as to avoid miscalculation or involvement. Since nearly eighty percent of all global maritime trade volume flows through the South China Sea, it is imperative to mitigate any risk to merchant transit and reaffirm the stability of key supply routes along the Spratly Islands archipelago. UNCLOS has failed to provide an effective framework for mediating Spratly Islands disputes. And while renewed foreign investment in the Filipino fleet ensures the safety of one of the U.S.’ strongest treaty allies in the region, it only enables the continuation of a dangerously militarized response strategy. Scholars have suggested alternative methods of resolution, such as designating the South China Sea as a semi-enclosed sea, which would nullify UNCLOS EEZ boundaries, supercede the concept of unilateral sovereignty, and instead force joint management of natural resources; but even the most robust proposition would still require the participation of all claimant states and the deescalation of currently heightened tensions. Diplomatic solutions derived and enforced by existing regional forums, like the Association of Southeast Asian Nations (ASEAN), offer the least escalatory path forward in light of deteriorating bilateral relations between the U.S. and PRC and the rise of maritime misbehavior in the archipelago. Hence, claimants of the Spratly Islands must act swiftly to ensure stability in the South China Sea—safeguarding their shared interests in peace and economic prosperity by collectively leveraging diplomatic power to counter aggression.