Exclusive Report: U.S. Marines Boost Anti-Submarine Warfare Skills in Philippine Sea to Counter China and Russia Submarines.

According to information published by the U.S. Department of Defense on August 8, 2025, U.S. Marines from the 31st Marine Expeditionary Unit (MEU) conducted advanced anti-submarine warfare training in the Philippine Sea using buoy-based underwater acoustic detection systems. The operation, carried out from ships of the USS America Amphibious Ready Group (ARG) with support from the aircraft carrier USS George Washington (CVN 73) and its carrier strike group, aimed to strengthen the ability of U.S. naval forces to detect, track, and deter hostile submarines in one of the most strategically contested maritime regions in the world.
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A U.S. Marine Corps MV-22B Osprey from Marine Medium Tiltrotor Squadron 265 (Reinforced), 31st Marine Expeditionary Unit, launches from the aircraft carrier USS George Washington (CVN 73) while participating in anti-submarine warfare training alongside the USS America Amphibious Ready Group in the Philippine Sea on August 8, 2025. (Picture source: U.S. DoD)

A notable aspect of the exercise was the launch of an MV-22B Osprey tiltrotor aircraft from Marine Medium Tiltrotor Squadron (VMM) 265 (Reinforced), 31st MEU, directly from the flight deck of USS George Washington. This demonstrated the high level of interoperability between Marine Corps aviation and U.S. Navy carrier operations. While the 31st MEU is embarked aboard the USS America ARG, the inclusion of the George Washington in the training scenario provided additional deck space, logistical support, and integration opportunities with the Navy’s carrier strike group capabilities.

The MV-22B’s unique combination of vertical takeoff and landing capability with fixed-wing range and speed allows it to deploy sonobuoys over large ocean areas at high speed. In an ASW role, the Osprey can quickly position passive systems such as the AN/SSQ-53 DIFAR for covert listening and active systems like the AN/SSQ-62 DICASS for sonar pulse detection. By combining these buoys in coordinated patterns, Marines can detect, classify, and track submarines even in the Philippine Sea’s challenging acoustic environment with its deep waters, thermal layers, and high ambient noise levels.

The 31st MEU is the only continuously forward-deployed Marine Expeditionary Unit, based in the Indo-Pacific and structured as a rapid-response force with integrated infantry, aviation, and logistics elements. It is designed to conduct amphibious assaults, crisis response, and multi-domain operations. The USS America ARG, its primary sea base, consists of the amphibious assault ship USS America (LHA 6), an amphibious transport dock, and a dock landing ship, providing aviation, amphibious lift, and command-and-control capabilities.

The inclusion of the USS George Washington in this ASW exercise illustrates the growing integration between amphibious ready groups and carrier strike groups. Carrier-based aircraft and sensors can augment amphibious forces with expanded surveillance reach, while Marine aviation can adapt to carrier deck operations to support broader joint missions.

Conducting ASW training in the Philippine Sea is strategically vital. This region lies along critical global trade routes and is adjacent to flashpoints such as the South China Sea and Taiwan Strait. It is also an area of intense submarine activity from regional powers including China and Russia. Chinese nuclear-powered and diesel-electric submarines, some equipped with air-independent propulsion systems, are optimized for stealth and long-range operations, while Russian Pacific Fleet submarines such as the Akula and Yasen classes can operate at speed and depth with advanced weapon systems. The ability of forward-deployed Marines to deploy acoustic detection networks from versatile platforms like the MV-22B adds a rapid-response layer to the U.S. Indo-Pacific Command’s undersea surveillance and deterrence posture.

This exercise marks a step forward in redefining the Marine Corps’ role in maritime security. By integrating into anti-submarine warfare alongside the Navy’s most capable carrier forces, the 31st MEU and the USS America ARG demonstrate that expeditionary units can now contribute directly to undersea domain awareness and protection of high-value naval assets. The joint use of USS George Washington and USS America platforms in this operation highlights a future where amphibious and carrier forces work seamlessly to counter submarine threats in the Indo-Pacific battlespace.