Philippine troops have completed a new resupply and personnel rotation to the BRP Sierra Madre at Second Thomas (Ayungin) Shoal despite Chinese coast guard vessels jamming radio traffic around the disputed reef, Philippine security officials said. The mission on Friday brought food, fuel, and fresh navy personnel to the grounded ship, which the Philippines ran aground in 1999 to anchor its claim in the Spratly Islands. Officials cited by the Associated Press said Chinese units interfered with communications to frustrate monitoring by U.S. and allied aircraft that track these missions.
Second Thomas Shoal lies about 105 nautical miles off Palawan, within the Philippines’ exclusive economic zone under the U.N. Convention on the Law of the Sea. Manila turned the Sierra Madre into a fixed outpost by beaching it on the reef and stationing a small marine detachment on board. China, however, folds the shoal into its sweeping “nine-dash line” claim and has ringed it with coast guard and militia vessels that try to control access. In 2016, an arbitral tribunal in The Hague ruled that China’s historic-rights claims inside the nine-dash line have no legal effect and that several Chinese actions in Philippine waters were unlawful, in a case registered as PCA Case No. 2013-19. Beijing rejected the ruling and continues to apply its own coast guard law at sea.
Why Chinese Ships Jammed Philippine Communications
The radio jamming is part of a broader playbook. Technically, disrupting radios makes it harder for Philippine commanders to maneuver small boats near the reef while larger Chinese hulls shadow or block them, and it complicates real-time surveillance and evidence gathering by aircraft that record voice and data during each mission. Politically, it lets Beijing decide which sounds and images leave the scene.
The move builds on earlier use of blocking, ramming, and water cannon and on a June 2024 incident in which China Coast Guard personnel boarded Philippine inflatable boats, smashed communications gear, and injured several sailors, an episode analyzed by the Asia Maritime Transparency Initiative. Jamming is the next layer in that pressure campaign, keeping the outpost vulnerable while stopping short of open combat.
Root Cause and Risks for Filipinos
The root cause is a clash over which rules govern Ayungin. The Philippines treats the 2016 arbitration award and UNCLOS as the legal basis for its presence and resupply rights and views the shoal as part of its maritime entitlements. China rejects the award and applies its own coast guard law and new regulations across much of the South China Sea, treating large areas as “waters under China’s jurisdiction.” Updated coast guard rules that took effect in 2024 allow detention of foreign crews and seizure of vessels in such waters for up to 60 days, a change flagged by the Asia Pacific Foundation of Canada as “upping the ante” in disputed areas.
Within that framework, electronic jamming of a Philippine mission functions as “lawfare”: domestic statutes, backed by coast guard ships and technology, are used to turn contested seas into zones of unilateral policing despite an adverse international ruling.
For the marines on the Sierra Madre and the sailors who resupply them, every mission now unfolds under the threat of close passes, water-cannon drills, boarding, and electronic interference. Reporting on the June 2024 clash described severe damage to Philippine boats and a sailor losing a thumb while under orders not to brandish firearms, underscoring how quickly a logistics run can become a life-threatening confrontation. Polls now show that most Filipinos view China as the country’s main threat, prompting Manila to consider closer security cooperation with the United States and other partners.
If the standoff continues, routine jamming and aggressive interception raise the chance that a misheard order or steering error could trigger a collision with casualties, and any event that Manila and Washington read as an “armed attack” on a Philippine public vessel would test the U.S.–Philippines Mutual Defense Treaty. U.S. analyses of the 2016 ruling and subsequent Chinese behavior already highlight this risk.’ For now, the latest run shows that the Philippines can still reach its marines at Ayungin, but each mission has become a live test of law, deterrence, and restraint in one of the world’s most contested seas.
As Editor in Chief of The Maritime, I lead content development, interviews, and digital storytelling across our multimedia maritime platform. With over 10 years of experience in the maritime industry, I create and publish in-depth stories and video features that highlight key players, emerging trends, and operational realities across global shipping. Before launching The Maritime, I worked as a Vessel Operator at Imza Marine A.S., gaining hands-on commercial shipping and voyage operations experience. I also served as Marketing Communications Specialist at Gimas Ship Supply & Services, where I managed corporate communication, digital strategy, and industry outreach for shipowners and maritime clients. I hold a Master’s degree in Maritime Transportation Management from Istanbul Technical University and a Master’s degree in Publishing from Marmara University. My work is driven by the belief that the maritime world deserves strong, informed, and accessible media representation. I am committed to sharing the stories of maritime professionals and contributing to the sector’s visibility, knowledge exchange, and future development.
