China’s maritime militia of professional and civilian vessels increased its activity at Mischief and Whitsun reefs in 2025 while boosting its overall South China Sea presence to a record daily average of 241 boats, the Asia Maritime Transparency Initiative (AMTI) reported in February 2026.
The militia augments China’s People’s Liberation Army’s Coast Guard and Navy and expands the regime’s posture in the South China Sea. China illegally claims most of the sea and in recent years its ships have rammed, blocked, and fired water cannons and lasers at other nations’ civilian and government vessels to back its illicit sovereignty assertion, often within those countries’ internationally recognized exclusive economic zones.
Brunei, Indonesia, Malaysia, the Philippines and Vietnam also have claims in the resource-rich sea, which is a vital global trade route. The United States and its Allies and Partners oppose China’s incursions and support an international tribunal’s 2016 ruling that rejected Beijing’s expansive territorial contention in a case brought by Manila.
The AMTI used commercial satellite imagery to analyze militia activity at 12 far-flung reefs, according to the Center for Strategic and International Studies (CSIS), a Washington, D.C.-based think tank that commissioned the study. Researchers chose not to rely on ships’ automatic identification system (AIS) transmissions because some vessels don’t have AIS or crews turn them off, often to conceal the vessel’s location if engaged in illicit activity.
The maritime militia has two detachments, according to the AMTI. Professionals receive military training and directly support uniformed forces. They specialize in gray-zone tactics such as blocking, swarming, shadowing and surveillance. The other, larger group comprises fishing crews for whom militia duty is secondary. Their vessels, sometimes referred to as the Spratly Backbone Fishing Fleet, maintain a presence and respond when summoned by authorities.
The latter group of boats perhaps has “diminishing value,” the AMTI noted, because other nations increasingly realize the fleet’s mission is not entirely fishing.
The reefs surveyed include Scarborough Shoal and, to the southwest, Spratly Islands outcroppings including Fiery Cross Reef, Gaven Reef, Hughes Reef, Iroquois Reef, Johnson Reef, Mischief Reef, Sabina Shoal, Second Thomas Shoal, Subi Reef, Thitu Island/Sandy Cay and Whitsun Reef. China has dumped crushed coral on some of the reefs and installed military bases.
The AMTI’s 2025 tally of China’s maritime militia in the sea surpassed the previous high in 2024, when the average daily number of vessels was 232. The 2023 daily average was 195.
Mischief and Whitsun reefs accounted for nearly half of the 2025 total, with Mischief having the largest concentration of China’s maritime militia, the AMTI reported. While the China Coast Guard focused on Scarborough and Sabina shoals — flashpoints for China-Philippines maritime confrontations — the militia held positions at less-contentious reefs. Gaven, Iroquois and Thitu, for example, had higher daily average numbers of ships off their perimeters in 2025 than in previous years.