Second Thomas Shoal
The BRP Sierra Madre is falling apart. Her hull is peppered with holes large enough for waves to slosh through into the hold. Rust has consumed entire sections of her superstructure. She has not sailed under her own power in decades and never will again. Yet this 100-meter World War II-era landing craft, deliberately run aground on Second Thomas Shoal in 1999, remains an active-duty commissioned vessel of the Philippine Navy, manned by fewer than a dozen marines whose resupply missions regularly make international headlines. What sounds like the setup for an absurdist novel is, in fact, one of the most consequential territorial standoffs in the South China Sea.
A Calculated Grounding
Second Thomas Shoal, known as Ayungin in Filipino, sits 105 nautical miles west of Palawan in the heart of the Spratlys' Dangerous Ground. In 1994, China occupied Mischief Reef nearby, alarming Manila. Philippine president Joseph Estrada decided in 1998 to "as well put up our own structures." The following May, two Philippine ships, the BRP Sierra Madre and the BRP Lanao del Norte, were intentionally run aground on the shoal. China demanded both be removed. The Philippines towed away the Lanao del Norte but left the Sierra Madre where she sat. Estrada reportedly promised to remove her too. That promise was never kept. By 2014, the Philippines had declared the rusting vessel a "permanent installation," transforming a stopgap measure into an enduring assertion of sovereignty.
Running the Blockade
Keeping the Sierra Madre garrison alive has required ingenuity. Philippine supply ships have navigated Chinese blockades using shallow-water routes where China Coast Guard vessels, with their deeper drafts, cannot follow. In March 2014, when Chinese ships blocked two civilian supply boats, the Philippines resorted to airdropping provisions. On March 29, a supply ship with replacement troops reached the shoal by threading through coral shallows. The cat-and-mouse pattern has continued for years. In November 2021 and August 2023, China Coast Guard vessels used water cannons to block Philippine supply boats. In early 2023, a Chinese coast guard ship aimed what the Philippines described as a military-grade green laser at a Philippine vessel, temporarily blinding crew members. China denied the incident.
Agreements Made and Broken
The diplomatic layer is as convoluted as the maritime encounters. In 2017, under President Rodrigo Duterte, the Philippines accepted a gentlemen's agreement with China to maintain the status quo: no construction materials would be allowed to reinforce the Sierra Madre, in exchange for reduced Chinese pressure. When Bongbong Marcos succeeded Duterte, he said he was unaware of any such agreement. "If there was, I rescind it as of this moment," he declared in 2023, adding a year later that he was "horrified" by revelations about the deal. In April 2024, China announced a "new model" agreement for the shoal. Philippine Defense Secretary Gilberto Teodoro flatly denied any deal existed. A provisional agreement on supply missions was quietly reached in July 2024, its details kept secret, only to fray again within weeks.
The Reef Beneath the Ship
Second Thomas Shoal itself is a submerged reef near the center of Dangerous Ground. Its coral rim surrounds a lagoon with depths up to 27 meters, accessible to small boats from the east. Drying reef patches emerge at low tide on both sides. In July 2016, the Permanent Court of Arbitration ruled that Second Thomas Shoal is a low-tide elevation, meaning it generates no entitlement to territorial sea, exclusive economic zone, or continental shelf under the United Nations Convention on the Law of the Sea. The feature belongs, legally, to no one's sovereign territory. It falls within the Philippines' exclusive economic zone, granting Manila certain resource rights but not full sovereignty. This legal ambiguity is precisely what makes the Sierra Madre's presence so charged: the ship is the claim, and removing it would mean conceding the argument.
From the Air
Second Thomas Shoal (Ayungin) is at approximately 9.65°N, 115.85°E, southeast of Mischief Reef in the Spratly Islands. From altitude, the submerged reef appears as a pale oval against deep ocean, with the rusted hulk of the BRP Sierra Madre visible as a small dark shape on the reef rim. No airstrip exists. The nearest Philippine airfield is Rancudo on Thitu Island (~90 nm northwest). Puerto Princesa (RPVP) is approximately 200 nm east. Expect Chinese coast guard and naval vessel presence in the immediate vicinity.