(UPDATE) CHINA’S maritime militia deployed a record number of vessels in the South China Sea in 2025, particularly around key disputed reefs near areas of tension with the Philippines, according to a Washington-based research project that monitors maritime disputes and activities in Asia.
Satellite imagery analysis by the Asia Maritime Transparency Initiative (AMTI) found a daily average of 241 militia vessels operating across monitored reefs in 2025, slightly higher than the 232 recorded in 2024.
The figure represents the highest level observed since the group began systematic monitoring in 2021.
The militia fleet — composed of professional militia units and civilian vessels belonging to China’s “Spratly Backbone Fishing Fleet” — was detected in all reefs monitored by the initiative, although activity continued to shift toward Mischief Reef and Whitsun Reef, which together accounted for nearly half of the total observed vessels.
Researchers said tracking militia vessels remains challenging because most ships turned off their automatic identification system (AIS).
Instead, AMTI relied on commercial satellite imagery to count ships massing at key reefs.
The study expanded its dataset to 12 reefs with the addition of Mabini (Johnson) Reef, where satellite imagery revealed a moderate seasonal concentration of vessels east of the feature during the past year.
Most ships identified were believed to belong to the Spratly Backbone Fishing Fleet, which is numerically larger than the professional militia component.
For the study, researchers counted only vessels between 45 and 65 meters in length, a size commonly associated with Chinese militia trawlers and rarely seen among other fishing fleets or the China Coast Guard.
Satellite imagery was analyzed roughly four times each month at each reef, with gaps between observations filled using interpolation to allow comparison across locations.
Seasonal patterns remained consistent with previous years. Vessel presence was lowest from January to mid-February, rising after the Lunar New Year.
Two major surges were observed across most features — one in June and another in late November.
At Panganiban (Mischief) Reef, militia presence showed four separate peaks exceeding 200 vessels, reinforcing its role as a key staging point for monitoring disputed areas near the Philippines, including Escoda (Sabina) Shoal and Ayungin (Second Thomas) Shoal.
Julian Felipe (Whitsun) Reef displayed a similar seasonal trend, with vessel numbers peaking in the spring before dropping during the summer and early fall and rising again later in the year.
Other features recorded increased militia activity compared with previous years. Rozul (Iroquois) Reef showed higher peaks and a stronger baseline presence throughout 2025, while Pag-asa (Thitu) Reef experienced increases in both average and peak vessel counts despite reduced coast guard activity in the area. Burgos (Gaven) Reef maintained peak levels similar to those seen in 2024 but had a higher average daily presence.
In contrast, Kagitingan (Fiery Cross) Reef had a sharp drop in militia activity. After averaging 32 vessels per day in 2024, the reef had almost no observable militia presence in 2025, suggesting a possible redeployment of Chinese vessels rather than an overall reduction in militia operations.
The research also compared militia deployments with patrols by the China Coast Guard. Despite a record rise in coast guard presence around Bajo de Masinloc (Scarborough) Shoal, militia vessels remained relatively few in the area.
Analysts said this pattern suggests that Beijing relies more heavily on smaller but more capable professional militia units and coast guard ships to patrol disputed areas, while larger numbers of Spratly Backbone vessels remain anchored at safer locations such as Mischief and Whitsun reefs.
AMTI said the 2025 data mirrors patterns seen in 2024 but with slightly higher overall militia presence and a redistribution of vessels across eastern areas of the Spratly Islands.