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U.S. Strengthens South China Sea Presence with Australia and Philippines in New Trilateral Naval Activity.
The United States, Australia and the Philippines completed a Multilateral Maritime Cooperative Activity on 15 to 16 February 2026 inside the Philippine Exclusive Economic Zone in the South China Sea. The drill underscores Washington’s treaty commitments to Manila and reflects growing trilateral efforts to deter coercion and reinforce a rules-based maritime order.
On 16 February 2026, defence and military authorities from Australia, the Philippines and the United States announced the completion of a new Multilateral Maritime Cooperative Activity (MCA) conducted inside the Philippine Exclusive Economic Zone in the South China Sea. Taking place on 15–16 February, this first trilateral MCA of 2026 forms part of a broader effort to consolidate naval cooperation and uphold a rules-based maritime order in one of the world’s most contested seas. Against a backdrop of recurrent incidents between Philippine and Chinese vessels near disputed features, the operation highlights how Manila’s treaty alliance with Washington and its growing defence ties with Canberra are being translated into visible presence at sea. The activity was detailed in an official U.S. Indo-Pacific Command release dated 16 February 2026 and supported by imagery and captions published by the Defense Visual Information Distribution Service (DVIDS).
The United States, Australia and the Philippines conducted a coordinated two day maritime activity inside the Philippine Exclusive Economic Zone, reinforcing trilateral naval cooperation and signaling allied resolve in the South China Sea (Picture Source: Britannica / U.S. Indo-Pacific Command)
The MCA brought together a compact but capable surface and air task group operating within the Philippine EEZ. From Australia, the Royal Australian Navy deployed the Anzac-class frigate HMAS Toowoomba (FFH 156), supported by a Royal Australian Air Force P-8A Poseidon maritime patrol and reconnaissance aircraft. The Philippines contributed the Jose Miguel Malvar-class guided-missile frigate BRP Diego Silang (FFG 07) with its embarked AW109 helicopter, a mix of FA-50 light combat aircraft, A-29 Super Tucano, C-208B and Sokół search-and-rescue platforms from the Philippine Air Force, and the Teresa Magbanua-class patrol vessel BRP Teresa Magbanua (MRRV 9701) from the Philippine Coast Guard. The U.S. contingent centred on the Arleigh Burke-class guided-missile destroyer USS Dewey (DDG 105), which is forward-deployed as part of Destroyer Squadron 15 under U.S. 7th Fleet, complemented by a U.S. Navy P-8A Poseidon from Patrol Squadron 4. This mix of frigates, a major surface combatant, a large coast guard cutter and long-range maritime patrol aircraft gave the activity a genuinely multi-domain character, linking surface operations directly with air and maritime surveillance assets.
The drills included visual signaling, formation maneuvering, and replenishment-at-sea procedures, all conducted in accordance with international law and maritime safety standards. These serials are not high-visibility combat scenarios, but they are essential building blocks for any future combined operation, whether related to crisis response, maritime security or, in the extreme, high-end conflict. Visual information drills refine communications discipline, identification procedures and the exchange of tactical information across different national command, control and communications systems. Replenishment-at-sea training strengthens the ability of surface forces to remain on station for extended periods, an issue of particular relevance in the South China Sea where distances from home ports are significant for Australia and the United States. The presence of P-8A Poseidon aircraft from both the Royal Australian Air Force and the U.S. Navy also underscores the importance of shared maritime domain awareness and anti-submarine warfare skills in these waters, even when the primary focus of the MCA is on surface manoeuvre and logistics.
Beyond the immediate drills, the trilateral MCA served as a practical test of how far doctrines, tactics, techniques and procedures have converged after several years of intensified cooperation among the three armed forces. Multilateral and bilateral MCAs have become a regular feature of U.S.–Philippine naval interaction in the South China Sea, in some cases integrating aircraft carriers, cruisers and additional frigate and patrol forces, while previous multilateral editions have brought in other regional partners. In this iteration, Australia’s presence alongside the United States reflects not only its growing operational reach but also a political decision in Canberra to be visibly engaged in maritime security operations close to Philippine-claimed features, despite the likelihood of Chinese diplomatic or operational responses.
For Manila, the activity showcases the integration of its navy, air force and coast guard, illustrating how a modest but modernising fleet can plug into allied command architectures built around U.S. 7th Fleet and long-range maritime patrol aircraft. For Washington, the MCA acts as a practical demonstration of a distributed operational model in which surface combatants, patrol aircraft and partner platforms operate together close to Chinese-claimed waters while remaining anchored in a broader network of exercises and access arrangements, including Enhanced Defense Cooperation Agreement sites on Philippine territory.
The geostrategic weight of this MCA lies in where and when it took place. Conducted inside the Philippine EEZ in the South China Sea, the activity unfolded against a record of increasingly forceful actions by Chinese coast guard and maritime militia units against the Philippine government and civilian vessels, including the frequent use of water cannons, dangerous manoeuvres and collisions near Scarborough Shoal, Second Thomas Shoal and other contested features. Over the past two years, several Philippine patrol and supply missions have sustained damage and crew injuries as a result of these incidents, prompting Manila to publicise encounters, lodge diplomatic protests and seek stronger alignment with allies and partners.
In response, the United States has repeatedly reaffirmed that the 1951 Mutual Defense Treaty applies to armed attacks on Philippine public vessels, aircraft and armed forces anywhere in the Pacific, including in the South China Sea, thereby signalling that serious harassment of Philippine assets could have alliance implications. Operating a mixed Australian-Philippine-U.S. formation inside the Philippine EEZ in this context underlines that the Philippines is no longer patrolling these waters alone.
For Beijing, the image of an Australian frigate, a U.S. destroyer and Philippine navy and coast guard vessels sailing together in tight formation inside Philippine-claimed waters sends a layered message. It demonstrates that the South China Sea is no longer treated as a series of isolated bilateral disputes between China and individual Southeast Asian claimants, but increasingly as a shared concern for a network of regional and extra-regional partners. The choice of a multilateral MCA, rather than a unilateral freedom-of-navigation operation, allows the activity to be presented as partner-led and consensus-based, consistent with allied statements that they are upholding freedom of navigation and overflight rather than seeking confrontation.
At the same time, the presence of USS Dewey, a modern Arleigh Burke-class destroyer equipped for air defence, maritime strike and anti-submarine warfare, anchors the formation in a credible combat platform even though the drills themselves are framed as routine. The underlying signal is that any serious incident sparked by coercive actions against Philippine vessels would unfold in an environment where U.S. and, increasingly, Australian naval power is already closely integrated with Philippine forces.
Seen in the broader evolution of Indo-Pacific security, this trilateral MCA represents another step toward a more networked web of maritime partnerships and a gradual consolidation of trilateral and minilateral formats. It complements U.S.–Philippine bilateral MCAs, large-scale exercises such as Balikatan and other combined activities that have already brought together the Philippines and several key regional partners in operations within Manila’s EEZ. For allies and partners, repeated but relatively low-profile cooperative activities of this type help create a sense of operational normality that complicates any attempt to portray allied presence as exceptional or illegitimate. For China, the cumulative effect is a more crowded operating environment in which coast guard and maritime militia units must now take into account not only the possible responses of Philippine vessels but also the potential reactions of treaty allies whose ships and aircraft routinely share the same waters and airspace.
This latest Multilateral Maritime Cooperative Activity carries significance well beyond the two days of drills logged on the exercise schedule. By bringing together Australian, Philippine and U.S. surface combatants, coast-guard forces and air assets inside the Philippine EEZ, the three countries are refining the practical mechanics of operating together while clearly signalling their intention to uphold navigational rights and national maritime entitlements in the South China Sea. The choice of platforms, the emphasis on interoperability and the decision to publicise the event through official U.S. Indo-Pacific Command statements and DVIDS imagery underline a shared assessment that, in the current Indo-Pacific context, deterrence is built not only on high-end warfighting capabilities held in reserve, but also on the kind of routine, visible cooperation that activities like this multilateral MCA bring to contested waters.
Written by Teoman S. Nicanci – Defense Analyst, Army Recognition Group
Teoman S. Nicanci holds degrees in Political Science, Comparative and International Politics, and International Relations and Diplomacy from leading Belgian universities, with research focused on Russian strategic behavior, defense technology, and modern warfare. He is a defense analyst at Army Recognition, specializing in the global defense industry, military armament, and emerging defense technologies.