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Victorie Tissiné, Francesco Gallina, Elena Alice Rossetti, Iris Hautaniemi Forsberg, Dakota Johnston-Kana, WATCH/GSOC Team

Jennifer Loy, Chief Editor

April 1, 2024

US and Regional Allies Sailing Together in the South China Sea[1]


The South China Sea remains a key contested area, with several incidents involving the Chinese, Filipino, and Taiwanese navies occurring in the first months of 2024. Chinese assertiveness in the aerial and maritime domain, especially towards Taiwan and the Philippines, has increased regional volatility, tensions, and direct clashes, which prompted the US and its regional allies to deepen defense cooperation and coordination. Daily Threat Activity Reports by The Counterterrorism Group (CTG) Watch Officers’ collected cases underline Chinese activities against Taiwan, such as sending jets, balloons, and satellite launches over the island. In the maritime scenario, the China Coast Guard (CCG) and China-linked maritime militias enhanced patrolling, blocking maneuvers, and direct clashes against the Filipino navy; while Russia, a close China’s partner in the region, has executed two sea drills. The US and its regional allies, such as Japan, South Korea, and the Philippines, are enhancing their defense ties and coordinating their responses towards China and Russia’s activities, implementing new cooperation frameworks, such as the trilateral partnership between the US, Japan, and South Korea.[2] 

Based on the quantity, validity, and data verification, CTG assesses with HIGH CONFIDENCE that tensions and potential direct clashes between the different regional and global parties involved in the South China Sea will very likely increase, likely indicating the maritime domain as the main confrontational area. China will very likely continue to invest in developing its fleet to enhance its blue-water capacity, likely implementing a more aggressive approach near contested areas. The US and its regional partners will likely deepen common defense initiatives and strategies, such as joint training exercises and patrolling, which China will likely depict as perceived threats to its national interests. The upcoming US presidential election and future electoral changes in Asian allied countries will likely define a different degree of cooperation, with a roughly even chance of national priorities diverting attention from the established multilateral frameworks. The military build-up in the South China Sea and the presence of contrasting navies near contested areas will very likely increase the risks of clashes or unwanted incidents, likely pushing the US Navy and its allies to implement a steady and coordinated approach to counter China's assertiveness and safeguard the respect of the rule of law, territorial integrity, and the United Nations Convention on the Law of the Sea (UNCLOS) provisions.

Recent Events

In 2024, Chinese vessels in the South China Sea clashed with the Filipino navy on several occasions, trying to block their resupply missions near shoals, on which China continues to reclaim sovereignty after the 2016 Permanent Court of Arbitration in The Hague ruling in favor of the Philippines,[3] which China declared “null and void.”[4] These recent developments are part of the increased Chinese naval presence and assertiveness in the contested areas of the South China Sea. In December 2023, the Philippines reported 135 Chinese military vessels near Whitsun Reef/Julian Felipe Reef (claimed by both the Philippines and China).[5] US authorities reaffirmed their support for the Philippines and reinforced the coordination among allies in the Indo-Pacific. In December 2023, a trilateral call between the US, Japan, and the Philippines urged China to refrain from “unlawful” behavior;[6] and, in March 2024, the US expressed concerns for Chinese “destabilizing” actions, reaffirming US commitments towards the Philippines, based upon the Article IV of the 1951 US-Philippines Mutual Defense Treaty.[7] Association of Southeast Asian Nations (ASEAN) leaders, after the 2024 ASEAN-Australia Special Summit in Melbourne, reiterated their call for a peaceful and lawful approach to territorial disputes in the South China Sea: “We want a region where sovereignty and territorial integrity is respected. We strive for a region where differences are managed through respectful dialogue, not the threat or use of force. We seek a region where disputes are settled peacefully in accordance with the universally recognised principles of international law, including the 1982 United Nations Convention on the Law of the Sea (UNCLOS).”[8]

On March 5, the Chinese navy caused multiple collisions and employed water cannons against Filipino boats resupplying BRP Sierra Madre, a wrecked ship serving as a Filipino military outpost near the Ayungin Shoal/ Second Thomas Shoal (claimed by both the Philippines and China).[9] On March 23, the National Security Council of the Philippines denounced that the CCG and the People's Armed Forces Maritime Militia (PAFMM) attacked the Filipino ship Unaizah May 4 with water cannons and blocking maneuvers, causing injuries among Filipino crew members, material damages and delays to the resupply mission.[10] After this incident, the Filipino Department of Foreign Affairs summoned the Chinese Charge d’affaires to formally protest against Chinese actions, underlining that the Philippines cannot accept Chinese “aggressive actions” and “continued interference” in their exclusive economic zone.[11] On March 25, Philippine President Marcos signed an order to ask the National Maritime Council, which will coordinate multiple agencies, to delineate and implement an effective and unified maritime security strategy.[12]

China has displayed further assertiveness towards its nearest neighbor Taiwan. Since January 2024, China has tested Taiwan’s responsiveness at least eight times. The first displays of force came just a few days before the country’s general elections[13] when Taiwanese residents witnessed the presence of several spying balloons over the island.[14] Almost as to simulate an ideal offensive operation, on January 9, only one day after the balloon sighting, the People's Liberation Army (PLA) organized and conducted a large-scale combat drill involving its aviation and navy. This exercise allowed China to display its might and spread its message well beyond its regional scope.[15] Skirmishes continued by the end of January with China constantly maintaining four military vessels around Taiwan. This measure aimed at simulating a war scenario in which China installed a blockade to isolate the island.[16] On February 3, the tension rose again as the deployment of ten Chinese fighters and five warships into Taiwanese jurisdiction prompted the islanders to alert their own air and sea troops, as well as activate anti-air defense systems.[17] China continued trespassing into Taiwanese waters with its coast guard on February 18, and at least once more on March 16. The first direct sign of international support for Taiwan in 2024 came from the US on March 18, admonishing China for changing the status quo of the region and starting an avoidable conflict.[18]

The US is increasing cooperation and coordination with historical regional allies. In August 2023, the US, Japan, and South Korea committed to enhancing trilateral ties, thanks to the rapprochement between Tokyo and Seoul. This partnership deepens security and defense ties, and information sharing, and establishes a consultation hotline to coordinate a common response to potential crises. [19] The Spirit of Camp David, their joint August 2023 statement, underlined the partners’ common stance regarding the ongoing challenges in the Indo-Pacific region, stressing the importance of freedom of navigation and the rule of law. Concerning Chinese activities, the States declared: “We strongly oppose any unilateral attempts to change the status quo in the waters of the Indo-Pacific. In particular, steadfastly oppose the militarization of reclaimed features; the dangerous use of coast guard and maritime militia vessels; and coercive activities.”[20] The US and the Philippines increased their military ties in recent months, with the announced construction of four new US military bases in Filipino territory[21] and the US-Japan-Philippines leaders allegedly planned their first trilateral summit in April 2024.[22]

Apart from Chinese activities in the region, there has been extensive cooperation between China and Russia in the South China Sea. In 2023, several naval drills involving both China and Russia took place in the South China Sea, and the two countries increased military cooperation in the region since Russia’s invasion of Ukraine.[23] In January 2024, a Russian Pacific Fleet warship conducted an anti-submarine exercise in the South China Sea,[24] and in March 2024, a joint drill between Russia, China, and Iran took place in the Gulf of Oman, highlighting their expanding naval military cooperation worldwide and showcasing their naval weapons stockpile.[25]

Timeline of Activities in the South China Sea, January 2024-March 2024[26]


Clashes between Chinese and Filipino navy vessels together with the incidents between China and Taiwan, will almost certainly continue in the South China Sea in the coming months, likely resulting in injuries and material damage. Continued clashes will very likely increase tensions between the different parties involved in the region, with China on one side and the US, Japan, the Philippines, and other allies on the other. Any minor incident will very likely lead to an escalation between the involved parties. The Chinese government will very likely portray any miscalculations, mistakes, and firm rhetoric from the US and its allies as a provocation. They will almost certainly use these skirmishes to legitimize the use of force and an expanding presence in the area as a response. This will very likely lead to an arms race in the region and contribute further to the general geopolitical tensions between China and the US worldwide.

China will very likely keep its naval presence in the South China Sea, especially near the contested areas such as the Ayungin Shoal/Second Thomas Shoal, likely deploying CCG and PAFMM assets[27] to disturb and prevent the Philippines' navy from resupplying and patrolling its outposts. The frequency of clashes and direct actions, such as unsafe blocking maneuvers and the use of water cannons against the Filipino navy, likely suggests China's increasingly aggressive stance and combat readiness. The Philippines' navy will likely increase its naval presence to enhance deterrence and prevent the Chinese forces from blocking resupply missions and expanding their presence near the Filipino outposts. The militarization of these areas and the conduct of Chinese vessels very likely endanger the Philippines' assets in the region, likely causing direct clashes and the risks of material damage and injuries for Filipino ships and crews. There is a roughly even chance that these confrontations will threaten civilian activities nearby, such as commercial navigation and fishing activities, considering Chinese PAFMM ships will likely resort to hybrid warfare.[28]

The US, Japan, and South Korea will very likely deepen their trilateral partnership, likely increasing interoperability and joint exercises to show their unity and enhance their forces’ military readiness, as they declared they will conduct multi-domain military exercises yearly “to bring trilateral defense cooperation to unprecedented levels.”[29] Continuity in joint exercises, such as the US, Japanese, and South Korean trilateral drills in November 2023 and January 2024,[30] almost certainly boost coordination and cooperation at operational and tactical levels, likely enhancing effective communication and aligning procedures. Coordinating information sharing and asset deployment will very likely reduce potential miscommunication and smooth joint tasks, likely improving readiness and resource allocation. Trilateral maritime initiatives will likely allow a persistent deterrence in the South China Sea, likely dividing the burdens between participants and increasing local allies' capabilities in the sea domain. 

China will very likely perceive the deepening of the cooperation between the US and its Asian allies as a provocation and direct threat. The US involvement in what China sees as a “purely Asian dispute”[31] will very likely increase tensions with the West. This escalation will likely impact China’s assessment of the threats to its presence and sovereignty in the region, motivating it to take increasingly coercive measures and encouraging further military build-up in the region. The US-Philippines-Japan Triad will likely organize its efforts around the deterrence of China’s attacks, through the enhancement of maritime security capacities. Recent developments and China’s escalating behavior will likely prompt the security triangle to focus on expanding their cooperation and redefining their objectives. This will likely entail a clear shift beyond the initial focus of the alliance, North Korea, and aim directly at containing China’s assertive position. The redefinition of the Triad’s aims will very likely lead to the prioritization of military cooperation over shared political and economic ambitions, likely aiming to provide the Philippines with adequate military equipment and training to prevent and respond to future attacks.  

China will very likely turn any development or statement undermining its assertive position in the South China Sea against the Philippines and its allies. It will likely turn these perceived provocations to its advantage, accusing the other parties of escalation or misinformation. By portraying itself as the victim, China will likely try to justify the use of force in its responses to its rivals’ countermeasures, which China will very likely present to the public as deliberate threats to its regional position. Chinese adopted countermeasures will very likely take the form of assertive territorial claims, by reinforcing militarization and reiterating its attacks in the South China Sea.The upcoming presidential US elections and other future government changes in the US-allied countries will likely impact how each country defines and implements its national priorities, with a roughly even chance of creating a misalignment in the Indo-Pacific objectives and military strategies of each participant. Multilateral initiatives such as ASEAN, the US-Philippines-Japan Triad, or the trilateral US-Japan-South Korea partnership very likely depend on each administration's approach, as the renewed military ties between the US and the Philippines after Marcos’ electoral mandate prove.[32] Chinese assertiveness almost certainly fosters US/Philippines and South Korea/Japan cooperation, but there is a roughly even chance that Beijing will try to exploit historical grievances, likely recalling ancient Japanese/South Korean disputes in public speeches or cyber campaigns, to weaken this trend.

Future Implications

The Chinese army will likely use CCG and PAFMM assets, likely challenging detection and effective, lawful responses from the US and their allies. PAFMM vessels will very likely continue to patrol the Ayungin Shoal/Second Thomas Shoal and support CCG actions against the Filipino resupply missions. Some militia vessels’ resemblance to civilian fishing boats will very likely delay a positive identification as militia vessels, likely increasing PAFMM's freedom of movement. These militias will very likely offer China plausible deniability, likely ensuring PLA practical advantages such as blocking resupply missions, while officially denying its involvement, especially in case of incidents. Chinese dual-strategy will likely solicit a more coordinated monitoring and information-sharing system between the US and its allies to track potential militia-linked ships at the early stage of their activities. Should incidents between the US or its allies and PAFMM occur, there is a roughly even chance that China will portray militia men as civilian fishermen, likely accusing Western allies of attacking unarmed civilians.

China will very likely contest Balikata, a drill between the Philippines and the US, alongside Australia and France planned for April 2024,[33] likely accusing the participants of threatening Chinese sovereignty. China will almost certainly underline that the exercise will take place in the Palawan province, an area where Filipino and Chinese ships clashed, likely defining this choice as a direct provocation. There is a roughly even chance that China will try to impede the part of the drill in these areas by placing  PAFMM vessels or floating barriers, likely increasing local tension between the Chinese PAFMM and the US Asian allies. Direct clashes between Chinese vessels and the US-allied navies remain unlikely, but Beijing's shadowing maneuvers against the Philippines’ partners and the deployment of naval assets near the drill’s declared locations have a roughly even chance of causing unforeseen incidents.

Japan will very likely increase its importance as the key US ally in the Indo-Pacific, considering its new posture regarding arms exports and the alleged possibility of the US restructuring the Indo-Pacific armed forces’ command. Japan will very likely continue to invest in and deploy long-range counter-strike assets,[34] likely enhancing defensive capacity on its territory and over the Taiwan Strait, and improving deterrence capabilities against Chinese assertiveness. Japanese plans to implement its first joint operational command and the potential enhanced structure of the US command in Japan[35] almost certainly underline Japanese significance in the security architecture of the Indo-Pacific and both countries’ long-term commitment to deepen security ties. China will very likely read the new Japanese posture as a threatening event, likely disseminating a narrative that portrays China as a peaceful power in contrast with a Japanese military build-up, with a roughly even chance of drawing a parallel to Japanese XXI century history. This campaign will almost certainly target South Korea, likely aiming at increasing Japanese negative perception and mining the actual Seoul-Tokyo rapprochement.

The next US presidential elections will very likely play a role in what will happen in the South China Sea in the next months. Given that both candidates served as US Presidents, it is possible to assess that Trump’s victory would very likely change the current geopolitical and diplomatic dynamics between the US and both its allies and competitors. Biden's second term will almost certainly ensure the US will continue supporting its partners and reaffirm the focus on countering Chinese assertiveness. Trump's prioritization of the US well-being and safety in his domestic and foreign policies implies a roughly even chance of seeing the US limiting the cases in which it will deploy its navy to defend its allies, or at least decrease the deterrence level it currently exercises on China. Conversely, the Biden administration has strengthened in the last four years economic, political, and military ties with all its regional allies, and has repeatedly manifested its intent to intervene in case of an attack against them. In the case of Biden’s victory, this cooperation process will almost certainly deepen and will make a Chinese offensive in the area less likely during his next term. It remains unlikely that China will forcefully claim territorial sovereignty until the next US elections, as it would likely increase the consensus for the incumbent US presidency.  

The Counterterrorism Group’s (CTG) PACOM, NORTHCOM, Weapons and Tactics (W/T), and WATCH/GSOC Teams will continue to track developments concerning ongoing escalation in the South China Sea. The teams will monitor daily events and analyze their potential impacts internally and externally. CTG will continue to follow the clashes between Chinese and Philippine navy vessels, the incidents between China and Taiwan, and the reaction from their allies. CTG will monitor Chinese and the US rhetoric and make future assessments of the stability of the region. CTG teams will provide recommendations to involved parties based on the most recent developments.

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[1] Sea Shapes, by Navy Petty Officer 3rd Class Nicholas Huynh, licensed under Public Domain

[3] PCA Case Nº 2013-19. IN THE MATTER OF THE SOUTH CHINA SEA ARBITRATION, The South China Sea Arbitration, July 2016, 

[4] Spokesperson: China neither accepts nor recognizes so-called award on South China Sea arbitration, China’s State Council Information Office, July 2023, 

[5] Philippines accuses China of swarming reef in South China Sea, BBC News, December 2023, 

[6] Readout of National Security Advisor Jake Sullivan’s Call with the National Security Advisors of Japan and the Philippines, The White House, December 2023, 

[7] U.S. Support for the Philippines in the South China Sea, U.S. Department of State, March 2024, 

[8] ASEAN-Australia Leaders’ Vision Statement – Partners for Peace and Prosperity, ASEAN, March 2024,,elbourne-declaration/ 

[9] U.S. Support for the Philippines in the South China Sea, U.S. Department of State, March 2024, 

[10] Armed Forces of the Philippines, X, March 23, 2024, 

[11] Statement Released by the DFA Spokesperson, Republic of the Philippines - Department of Foreign Affairs, March 2024, 

[12] Philippines boosts maritime security as China tension rises, Reuters, March 2024,

[14] Ignoring Taiwan's complaints, more Chinese balloons spotted over strait, Reuters, January 2024, 

[15] China holds large-scale joint strike drills aimed at Taiwan, AP News, January 2024, 

[20] The Spirit of Camp David: Joint Statement of Japan, the Republic of Korea, and the United States, The White House, August 2023, 

[21] Philippines, U.S. Announce Locations of Four New EDCA Sites, U.S. Department of Defense, April 2023,

[22] First U.S.-Japan-Philippines trilateral to address China's 'gray zone' tactics, Nikkei Asia, April 2024, 

[23] China prepares for naval drills with Russia in sign of continuing support amid Ukraine conflict, AP News, 

[25] Iran, Russia and China show off their ships in a joint naval drill in the Gulf of Oman, AP News, March 2024, 


[28] Military Must Be Ready to Confront Hybrid Threats, Intel Official Says, U.S. Department of Defense, September 2019, 

[30] Japan, Republic of Korea, U.S. Navies Partner in Trilateral Maritime Exercise, America’s Navy, January 2024, 

[31] Philippine leader warns of countermeasures in response to Chinese aggression at sea, ABC News, March 2024, 

[33] Philippines, US to hold military drills in islands facing South China Sea, Taiwan, Reuters, March 2024, 

[34] “National Defense Strateg” Provisional Translation, Japan Ministry of Defense., December 2022, 

[35] China eyes US-Japan security upgrade plan, Voice of America, March 2023, 



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