US maintaining strong military presence in South China Sea, says report

The United States maintained a high-intensity military presence in the South China Sea and surrounding areas in 2025, with close-in reconnaissance, joint exercises and alliance-based operations increasing notably despite military pressures in other regions, according to a report released on Friday.

The annual report, issued by the Beijing-based South China Sea Strategic Situation Probing Initiative, found that although the US Navy and Air Force faced constraints because of tensions in the Middle East and other theaters, Washington sustained a strong military presence in and around the South China Sea.

Military experts said the findings suggest that US operations are aimed not only at maintaining a regional presence, but also at strengthening deterrence, intelligence collection, alliance coordination and battlefield preparation.

The initiative, which has published annual assessments based on open-source data since 2019, said US military activities targeting China in the South China Sea have risen sharply since 2009.

The study found that US military operations showed mixed trends in 2025. Activities by carrier strike groups, amphibious ready groups, ocean surveillance ships and bombers showed signs of fatigue, largely because of deployments to global hotspots and constraints on US manufacturing, particularly shipbuilding capacity. The frequency of so-called "freedom of navigation" operations also declined.

However, close-in reconnaissance, drills and training, and joint operations with allies and partners increased significantly. Unmanned platforms accounted for much of the increase, with large US unmanned reconnaissance aircraft making up about 30 percent of US close-in aerial reconnaissance sorties targeting China in the South China Sea.

MQ-4C Triton and MQ-9 Reaper drones deployed in Okinawa, Japan, and at Clark Air Base in the Philippines have become key contributors to increased reconnaissance because of their long range, endurance and lower operational risk, the report said.

Hu Bo, director of the South China Sea Strategic Situation Probing Initiative, said the growing use of unmanned platforms could increase the risk of encounters with manned aircraft because communication between unmanned and manned systems is less direct. China should also expand its own use of unmanned platforms, he said, because relying on manned platforms to counter drones would be inefficient and uneconomical.

The report said US reconnaissance aircraft conducted about 1,200 sorties in the South China Sea in 2025, while ocean surveillance and survey vessels operated for 197 ship-days.

Reconnaissance flights were more frequent at the beginning and end of the year, peaking in November, the assessment noted. Sorties typically increased when China conducted major military deployments or when large US formations operated in the South China Sea.

After the CNS Fujian aircraft carrier left the port in Sanya, Hainan province, for training in the South China Sea in November following its commissioning earlier that month, US close-in reconnaissance became more frequent and more intensive, the report said.

Military commentator Zhang Junshe said the increase in reconnaissance aircraft, warships, submarines and carrier group operations reflects Washington's latest national security and defense priorities, with the Western Pacific and the Asia-Pacific remaining key strategic areas.

He said the US is seeking to strengthen deployments along the so-called first island chain, maintain pressure on China and rally allies such as Japan and the Philippines. Increased operations are intended to support allies, especially the Philippines, while collecting intelligence on China's military activities.

Zhang said previous Philippine provocations near Chinese reefs were often accompanied by US P-8A patrol aircraft, drones and naval vessels, indicating that Washington was providing both political backing and intelligence support.

The report also highlighted growing US reliance on bases in the Philippines. Traditionally, US aerial reconnaissance missions in the South China Sea have departed mainly from Kadena Air Base in Okinawa and entered the region through the Bashi Channel. In recent years, however, US intelligence, surveillance and reconnaissance assets have increasingly shifted to forward bases in the Philippines, with flights departing directly from those bases becoming more frequent.

At least 11 US nuclear-powered submarines operated in the South China Sea and surrounding waters in 2025, demonstrating a deterrent role, the report said.

US bombers carried out seven deployments involving 13 B-52H and B-1B sorties, fewer than in previous years. The study said US bomber operations in the Western Pacific are undergoing structural adjustments through temporary rotations, including B-1B deployments to air bases in Japan.

The US Navy deployed four carrier strike groups to the South China Sea on nine occasions in 2025. Three of the groups were later redeployed to the Middle East, making the South China Sea a transit point for carrier resources between the US "Indo-Pacific" Command and US Central Command.

Compared with previous years, US carrier strike groups made fewer routine port visits to countries bordering the South China Sea because of tensions in the Middle East and pressure on global deployments. At the same time, they increased joint patrols and exercises with allies, the report said.

Zhang said the increased reconnaissance activities also serve battlefield preparation purposes. As China's aircraft carriers and submarines have become more active in the South China Sea, the US has intensified targeted reconnaissance, including efforts to study underwater conditions, hydrology, weather and seabed terrain, and to build anti-submarine and submarine-detection networks.

The report said the US and its allies accelerated military network-building in the South China Sea, with the Philippines serving as a key node. Under existing US-Philippines defense frameworks, the US advanced base upgrades, expanded joint training, institutionalized defense dialogue, and strengthened the forward deployment of missiles and other key military equipment.

Vessels and aircraft from Japan, Australia, Canada, France and other US allies and partners also frequently entered the South China Sea for joint or multilateral operations, gradually forming a forward deployment network centered on the US, according to the report.

The report recorded 122 major exercises by the US and its allies from the Philippine Sea to Australia. It said the drills featured unprecedented multilateral participation, broader integration of unmanned systems and long-range firepower, and scenarios more closely aligned with specific South China Sea flashpoints.

Hu said such exercises do not substantially change the regional military balance or pose a major military threat to China, but they have negative political and diplomatic implications.

"Their main effect is to heighten tensions and encourage the Philippines to continue actions targeting China," he said.

Zhang said the growing involvement of countries outside the region under US coordination would complicate the South China Sea issue, encourage the Philippines to take more provocative actions and undermine regional peace and stability.

Looking ahead, the report said the Asia-Pacific will remain a key strategic direction for the US military regardless of future policy adjustments or developments in other global hotspots, and Washington is likely to maintain its military presence and operations in the South China Sea and surrounding areas.

Hu said the overall US strategy in the South China Sea has not changed significantly since 2009, but many activities have reached a ceiling because of pressure from other theaters and shortages of US military platforms, especially warships. This has led to overdeployment and fatigue within the US military, he said.