By Wu Qiaoxi | 2025-12-24

China is transforming its outposts on Fiery Cross, Mischief and Subi reefs into sophisticated hubs for electronic warfare and intelligence, according to a new study by the Asia Maritime Transparency Initiative (AMTI), a project of the Washington-based Center for Strategic and International Studies.

In a report released in early December, AMTI said that since 2022, China has added new radar stations, antenna arrays and multiple electronic warfare systems on the three reefs.

"These upgrades underscore the fact that a major function of China's bases is to provide unparalleled ISR [intelligence, surveillance and reconnaissance] coverage of the South China Sea," the report said. The facilities support China's coast guard and navy during peacetime operations and allow Beijing to "contest the use of the electromagnetic spectrum by others in the event of a conflict," directly affecting communications and navigation.

Antennas and radar

Satellite imagery analysis shows that between 2023 and 2024 China installed at least six fixed monopole-antenna arrays on the three reefs, all oriented toward open water. The equipment appears linked to vehicle-mounted sensing and communication systems and is likely intended for electronic jamming or direction finding, according to the report.

In early 2025, China added two radomes (protective domes for radar) on Subi Reef. Their design closely matches that of radomes that have been present on Fiery Cross Reef and Mischief Reef since 2017. The similarity suggests Beijing is building a broad, overlapping radar network capable of persistent monitoring of key parts of the South China Sea.

In addition to these electronic warfare upgrades, Mischief Reef has seen new coastal emplacements since 2023. The fortified positions could support the deployment of mobile weapon systems such as artillery or multiple rocket launchers, further expanding the reef's military role.

Rivalry with Manila

China's push comes amid frequent confrontations with the Philippines near Second Thomas Shoal and Scarborough Shoal that increase demand for maritime surveillance and counter-surveillance capabilities.

The Spratly outposts are situated roughly 600km from China's nearest major military bases, raising the cost of sustained monitoring and patrols. At the same time, countries including the Philippines and Vietnam are enhancing their own South China Sea surveillance.

The Philippines has accused China's military of firing three flares from Subi Reef on December 6 toward a Philippine aircraft conducting maritime domain awareness operations in the South China Sea.

"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," the Philippine coast guard said.

To improve maritime surveillance and intelligence gathering, Manila has requested the deployment of unarmed MQ-9A drones from the United States. A temporary deployment began last month.

In October, US War Secretary Pete Hegseth proposed the creation of joint unmanned aerial and undersea systems among Southeast Asian nations, aiming to improve monitoring efficiency while reducing risk and cost.

Rivalry with Hanoi

Another study published in August said Vietnam is also accelerating land reclamation in the South China Sea, with total scale expected to surpass China's. The development has raised questions about whether Hanoi will replicate Beijing's intelligence and electronic surveillance model.

China claims sovereignty over more than 80% of the South China Sea, a claim rejected by an international tribunal ruling in 2016.

Beijing began large-scale land reclamation in the South China Sea in 2013, followed by rapid militarization that included runways, barracks, missile platforms and radar systems. In 2016, China openly landed a military aircraft on Fiery Cross Reef, despite international disputes over ownership of the reef. It was the first such landing on any of the three disputed reefs -- Fiery Cross, Mischief and Subi -- in the area, according to Time magazine.