A U.S. think tank reports that China has upgraded electronic warfare and surveillance systems across its major Spratly Islands bases, including Mischief, Subi, and Fiery Cross reefs.
According to the Asia Maritime Transparency Initiative, China has deployed fixed monopole antennas and vehicle-mounted units equipped with jamming and sensing systems at three bases.
“These upgrades underscore the fact that a major function of China’s bases is to provide unparalleled ISR coverage of the South China Sea, supporting the operations of China’s coast guard and navy in peacetime and allowing Beijing to contest the use of the electromagnetic spectrum by others in the event of a conflict,” the report reads.
The think tank noted that the Chinese buildup comes as Vietnam accelerates its own construction in the Spratly Islands. China claims nearly the entire South China Sea, despite overlapping claims from countries including the Philippines and Vietnam.
Over the weekend, Chinese forces fired three flares from Subi Reef at a Philippine aircraft conducting a maritime domain awareness flight in the South China Sea.
PCG and BFAR Conduct Maritime Domain Awareness Flight Over Kalayaan Island Group
The Philippine Coast Guard (PCG) in collaboration with Bureau of Fisheries and Aquatic Resources (BFAR), conducted a routine Maritime Domain Awareness (MDA) flight today over the Kalayaan Island… pic.twitter.com/baGPyzEFSi
— Jay Tarriela (@jaytaryela) December 6, 2025
“The Bureau of Fisheries and Aquatic Resources aircraft recorded video footage of three flares fired from the reef toward the aircraft during its lawful overflight,” said Philippine Coast Guard spokesperson Commodore Jay Tarriela.
Last month, the United States temporarily deployed MQ-9A Reaper drones to the Philippines to enhance the country’s maritime surveillance and intelligence-gathering capabilities.
