Southeast Asia in the South China Sea: Standing Alone, Together
By: Major Ron J. Lienhardt, USMC
Disclaimer: The views expressed are those of the author and do not necessarily reflect the official policy or position of the U.S. Military Departments, the Department of Defense, or the U.S. Government.
In April 2023, the Chinese Coast Guard prevented a Filipino patrol from resupplying soldiers aboard the Philippine Republic Ship (BRP) Sierra Madre near the Second Thomas Shoal.[1] Neither the United States, which has a mutual defense treaty with the Philippines, nor the United Nations Security Council responded. That is because the Philippines faces China’s strategy of pressure below the threshold of armed conflict.[2] China applies this same strategy on other regional states including Vietnam, Brunei, Indonesia, and Malaysia. Robert Kaplan argues this strategy attempts to gain control by normalizing activities and eroding the political will to resist.[3] Bill Hayton elaborates, writing that Beijing invokes questionable historical interpretations to increase coercion and normalize its presence.[4] The result turns contested waters into a fait accompli, one confrontation at a time. These states cannot avoid great power competition or allow conflicting claims among themselves to leave them vulnerable to external maneuvers.[5] They must act in coordination to ensure their sovereignty.
China offers only debt and dependency.[6] Beijing uses diplomatic and economic incentives, as well as coercion, to foster dependence, leveraging economic ties to deflect criticism. The Belt and Road Initiative has funded infrastructure projects throughout Southeast Asia, but the terms of those investments, such as high interest rates and Chinese operational control, have raised significant sovereignty concerns.[7]
The United States expands and contracts its commitments based on concerns elsewhere and domestic political trends. The current U.S. National Defense Strategy “does not conflate Americans’ interests with those of the rest of the world—that a threat to a person halfway around the world is the same as to an American.”[8] It also refers to a “decent peace, on terms favorable to Americans but that China can also accept.”[9] When combined with America’s call for increased partner burden-sharing, the opportunity exists for regional states to take bold actions before China creates a status quo that remains acceptable to U.S. interests but at their expense.[10]
The smaller regional states must look to one another to protect their economic, political, and security interests. They also should seek support from the United States, and pursue stronger partnerships with Japan, South Korea, Australia, and Europe. This will build a distributed network of partnerships that more closely share geographical and security concerns.[11] These states cannot secure sovereignty in the South China Sea through legal victories or dramatic military standoffs.[12] They can most effectively secure sovereignty together, not alone, through presence, resolve, and legitimacy.
External partnerships are important, but their inherent conditionality comes at the expense of the state whose security depends most heavily on that partnership. A strategic framework dependent on sustained great power commitment also remains vulnerable to shifting policy and politics. The smaller states must mitigate this fragility and view external partnerships as individual pillars, not as the foundation.
The Legal Fiction of Territorial Claims
Any coherent strategy must also consider the legal landscape. James Benoit’s Practical Guide to the Law of the Sea reinforces what arbitration has affirmed: sovereignty over maritime features does not automatically grant extensive maritime rights. Under the United Nations Convention on the Law of the Sea, only naturally formed islands capable of supporting human habitation or economic activity can create exclusive economic zones. Rocks that cannot support life only establish a twelve-nautical-mile territorial sea. Low-tide elevations and artificial islands do not generate any maritime claims.[13]
The 2016 tribunal case against China validated these principles, ruling that most features in the Spratlys and Paracels cannot legally support the maritime claims asserted by multiple parties. China rejected the verdict, but the legal framework remains binding in the international community. Historical claims, occupation, and administrative declarations cannot override the arbitration or UNCLOS.[14]
This legal landscape leaves a troubling strategic implication: Vietnamese, Filipino, and Malaysian territorial claims push the boundaries of what international law can uphold and are counterproductive.[15] Such competing claims, which prioritize individual state interests over regional security, hinder efforts to promote collective action, as each state must defend its own legal stance against both its neighbors and Beijing.[16]
China’s occupation and patrol campaign exploits this fragmentation. Artificial islands do not establish lawful maritime zones, but they create powerful perceptions of permanence and control. Beijing’s aims not to win arbitration, but to redefine sovereignty by altering how the world perceives ownership. The affected states must oppose these efforts not only legally, but through presence to combat China’s claim to legitimacy.
The Case for Intra-Regional Solidarity
The mandala, rooted in Southeast Asian political history, depicts authority as spreading outward through networks of relationships rather than being imposed from fixed territorial centers.[17] This tradition sees power as relational and layered, not binary and hierarchical. Today, it can serve as a security model that aligns with both the region’s politics and the modern strategic environment better than the modern claim and dispute framework do.
In the South China Sea, a mandala of unity would mean the regional states look beyond their conflicting claims to focus on their common interests: responsible stewardship and preventing outsiders from taking control of waters that support their fisheries, shipping, and security. Effective partnerships need frameworks that enhance partner capacity rather than rely on the strengths of external powers to ensure security.[18]
Such cooperation is practical. Malaysia and Brunei, who have managed overlapping claims in the Spratlys through bilateral arrangements, could formalize this cooperation as a model for others. Vietnam and the Philippines could establish protocols for maritime operations to combat harassment and reduce the operational tempo of their crews and equipment. Indonesia, though not a formal claimant in the Spratlys, could formalize collaboration with Malaysia in the Strait of Malacca and, in return, form a partnership to defend the specified rights granted by its claim of an exclusive economic zone near the Natuna Islands. The Balabac Strait, a key chokepoint between Malaysia and the Philippines that controls access to the South China Sea, has also long served as a route for illicit trafficking. Environmental protection agreements, bilateral maritime patrols, exercises on Palawan and Banggi Island, and agreements on data collection and information sharing would demonstrate a strong commitment that is currently missing.[19]
Even existing frameworks like the Association of Southeast Asian Nations (ASEAN) could provide an effective support structure. Currently, ASEAN faces difficulties in uniting on South China Sea issues despite Cambodia ratifying the United Nations Convention on the Law of the Sea in January 2026,[20] partly because Chinese influence prevents consensus. As such, a binding South China Sea Code of Conduct with China remains elusive.[21] ASEAN’s commitment to consensus, a sensible norm in most cases, remains structurally vulnerable when China pressures just one member.
Solidarity does not mean solving every issue. It means agreeing on a baseline: no unilateral concessions to great power coercion, no bilateral agreements that undermine regional consensus, and a shared commitment to transparency concerning activities and incidents at sea. The challenges of existing consensus mechanisms do not make solidarity impossible; they make alternative approaches necessary. Flexible partnerships targeting specific regional interests support the persistence needed to identify and report rogue activities.
Diversifying Partnerships: Japan, South Korea, and the European Union
Regional states must expand external partnerships alongside their internal ones. They understandably have an instinct to rely mainly on the United States, as Washington has treaty alliances with the Philippines and Thailand and maintains strong security ties with Singapore, Malaysia, Indonesia, and, increasingly, Vietnam. American maritime power remains vital for freedom of navigation in the region. However, America historically has demonstrated unpredictability in its commitments, and U.S. policy in the Indo-Pacific has fluctuated between engagement and withdrawal. This should motivate Southeast Asian states to build partnerships with other entities sharing similar security and economic interests while continuing their collaboration with the United States.
Japan offers an underutilized partnership. Tokyo has strategic interests in freedom of navigation in the region: about eighty percent of Japan’s energy imports transit these waters.[22] Japan’s Office of Security Assistance can enhance capacity-building programs for Southeast Asian maritime enforcement agencies by financing patrol vessels and providing training and technical assistance. Japan’s recent constitutional evolution has expanded the legal basis for security cooperation, and Tokyo has demonstrated a consistent commitment to regional engagement, unhindered by elections.
South Korea provides advanced capabilities while managing significant domestic security concerns. Seoul is a leading shipbuilder, an exporter of advanced maritime technology, and an advanced defense partner. Its geopolitical position, squeezed between China and an increasingly transactional United States, gives it a natural inclination toward the kind of distributed, multilateral security architecture that regional states require.[23] South Korean investments in Southeast Asian infrastructure, maritime surveillance technology, and defense-industry partnerships could provide material and political influence, thereby diversifying dependence away from any single partner.[24]
The European Union has a unique advantage: diplomatic influence, economic power, and normative legitimacy. EU members do not have territorial claims in the South China Sea nor first-order alliances apart from NATO commitments that could complicate their position. This provides a strategic benefit. The European Union’s Indo-Pacific strategy, adopted in 2021 and updated in 2025, clearly defines freedom of navigation and the rules-based maritime order as European interests.[25] France, Germany, and the Netherlands have all conducted freedom-of-navigation transits in the South China Sea in recent years. European investments in regional infrastructure, including ports, digital connectivity, and clean energy, can serve as an alternative to Chinese financing under terms that do not threaten sovereignty.
Deliberate strategic diversification provides the key for Southeast Asian states’ sovereignty. Southeast Asian states should build a security network so distributed that no single defection can cause its collapse. This involves engaging Japan, South Korea, and European partners not as supplements to existing American relationships, but as complementary partners, each with its own roles, institutional channels, and incentives to stay engaged.
An Asymmetric Approach Across All Instruments of Power
An asymmetric approach spanning all instruments of national power and involving a broad network of partners can achieve a collective parity to challenge China’s coercive strategy and make it costly enough to prevent escalation and maintain regional stability.[26]
Diplomatically, regional states should commit to a coordinated campaign to ensure they document, publicize, and discuss at multilateral forums[27] China’s coercive actions. Beijing currently calculates that it can manage incidents such as the use of water cannons, laser targeting, and dangerous maritime intercepts. However, when documented regionally and publicized internationally, they create a pattern of behavior that can damage China’s reputation. Japan and South Korea can strengthen this effort through their extensive diplomatic channels. European partners can also raise these issues in forums where China seeks economic cooperation elsewhere.
Informationally, the cognitive dimension of conflict has only recently begun to receive the attention it deserves. Cognitive warfare aims to shape perceptions of legitimacy, not just military operations.[28] Koichiro Takagi has documented how Chinese strategists are learning from the information environment of the war in Ukraine, where messaging has been as important as tactical outcomes.[29] Regional states should develop their own shared narrative to inform and influence both domestic and international audiences through transparent incident reports, counter-messaging, and public diplomacy that highlight regional solidarity as the expected response to coercion.
Militarily, regional states should not strive to match China’s capabilities, but to increase the cost of China’s coercive actions.[30] This aligns with Julian Corbett’s adage that “the object of naval warfare must always be directly or indirectly either to secure the command of the sea or to prevent the enemy from securing it.”[31] A capable multilateral maritime force, backed by advanced training, equipment, and partners, can complicate gray-zone operations without triggering escalation. Interoperability exercises with external participants build operational familiarity and international credibility. They also reduce the operational tempo of individual maritime forces.
A stronger security partnership among the regional states will also better prepare them for a possible conflict between the United States and China. The current American National Security and Defense Strategies have specifically called for increased burden sharing among partners and allies. A mandala of interoperable regional partners with shared security and economic interests would provide precisely support international order and security in the emerging security environment.
Economically, protecting natural resources and diversifying trade and investment ties help build strategic resilience. China has long exploited resources and used economic dependence and bilateral trade agreements to influence regional matters.[32] Reducing that dependency through stronger intra-regional trade, deeper economic integration with regional middle powers, and targeted European investment reduces Beijing’s ability to use economic pressure as a coercive tool.[33] Doing so would not commit Southeast Asian states to economic warfare with China, but rather represent prudent portfolio management applied to security when combined with a more diverse network of security partners.
The Long Game
Dr. Ian Storey noted two decades ago that Southeast Asian states manage their relationship with China through economic integration to temper Beijing’s behavior, while relying on U.S. security as a hedge.[34] That approach has not succeeded. China has become more assertive as its economic ties in the region have strengthened. Regional states cannot continue to mistake accommodation for strategy.
Southeast Asian states should not choose a path forward based on preparation for confrontation, but rather one that builds a resilient regional order grounded in international law, sustained through partnerships, and guided by the collective resolve of states that stand to gain more from unity than from bilateral deals. They should not frame such an approach as a military alliance, but rather as a commitment to make China’s coercion visible, their resistance normal, and the isolation of any single state structurally difficult.
Great powers have historically acted unpredictably or seesawed between competing interests. The regional states must now act accordingly. They have a choice between strategic passivity and the patient construction of a whole-of-government security framework strong enough to outlast any great power’s attention span, not between dependence on the United States or submission to China.
In the South China Sea, sovereignty must belong to the states that show up, day after day, in the waters they share together, not to the state that builds the biggest artificial island or brandishes the strongest force.
About the Author:
Major Ron J. Lienhardt is a Marine Corps infantry officer and Southeast Asia foreign area officer currently serving as operations officer of the U.S. Military Group at the U.S. Embassy in Kuala Lumpur. Before this assignment, he commanded a rifle company and served as fires and effects coordinator as 1st Battalion, 3rd Marines transitioned into 3rd Littoral Combat Team.
[1] Verma Simonette and Joel Guinto, “’Dangerous manoeuvres’ in China and Philippines’ cat-and-mouse sea chase,” BBC, 28 April 2023, https://www.bbc.co.uk/news/world-asia-65421115.
[2] Global Conflict Tracker, Council on Foreign Relations, https://www.cfr.org/global-conflict-tracker/conflict/territorial-disputes-south-china-sea, and “Malaysia to investigate media leak of classified diplomatic note from China,” Reuters, 4 September 2024.
[3] Robert D. Kaplan, Asia’s Cauldron: The South China Sea and the End of a Stable Pacific (New York: Random House, 2014).
[4] Bill Hayton, The South China Sea: The Struggle for Power in Asia (New Haven: Yale University Press, 2014).
[5] Asia Maritime Transparency Initiative, Center for Strategic and International Studies, https://amti.csis.org/maps/.
[6] Where the U.S. Is Building Up Military Force Near Iran, New York Times, https://www.nytimes.com/2026/01/29/us/politics/trump-iran-us-military-maps.html and Bernd Debusmann, “U.S. aircraft carrier group arrives in the Caribbean,” BBC, 12 November 2025 and Keith Barney et. al., “Trapped in debt: China’s role in Laos’ economic crisis,” Lowy Institute, 13 April 2025, https://www.lowyinstitute.org/publications/trapped-debt-china-s-role-laos-economic-crisis.
[7] Belt and Road Tracker, Council on Foreign Relations, https://www.cfr.org/articles/belt-and-road-tracker, and Asia Maritime Transparency Initiative, “A Tale of Two Reams: Questions Remain at Cambodia’s Growing Naval Base,” Center for Strategic and International Studies, https://amti.csis.org/maps/.
[8] National Defense Strategy, p. 8, https://media.defense.gov/2026/Jan/23/2003864773/-1/-1/0/2026-NATIONAL-DEFENSE-STRATEGY.PDF.
[9] National Defense Strategy, p. 10.
[10] Adinda, “China’s ‘Salami-Slicing’ Strategy, How Beijing is Redrawing the Map of the South China Sea,” Modern Diplomacy, 24 November 2025, https://moderndiplomacy.eu/2025/11/24/chinas-salami-slicing-strategy-how-beijing-is-redrawing-the-map-of-the-south-china-sea/.
[11] Ron J. Lienhardt, “Fort Drum Shows How States Can Push Back on China’s Maritime Aggression,” War on the Rocks, 22 September 2025.
[12] Caitlin Campbell and Nargiza Salidjanova, “South China Sea Arbitration Ruling: What Happened and What’s Next?” U.S. – China Economic and Security Review Commission, 12 July 2016, https://www.uscc.gov/research/south-china-sea-arbitration-ruling-what-happened-and-whats-next, and Scott Smith, “A Chinese Collision at Sea Raises Important Questions,” U.S. Naval Institute, August 2025, https://www.usni.org/magazines/proceedings/2025/august/chinese-collision-sea-raises-important-questions.
[13] James P. Benoit, A Practitioner’s Guide to the Law of the Sea (Leiden: Brill/Nijhoff, 2020).
[14] “The South China Sea Arbitration (Philippines v. China),” Permanent Court of Arbitration, Award of 12 July 2016, PCA Case No. 2013-19, https://pca-cpa.org/en/cases/7/.
[15] Raul Pedrozo, “China versus Vietnam: An Analysis of the Competing Claims in the South China Sea,” Center for Naval Analyses, 2 August 2014, https://www.cna.org/analyses/2014/china-versus-vietnam.
[16] “Malaysia complains to Vietnam over South China Sea reef expansion, sources say,” Reuters, 4 November 2024, https://www.reuters.com/world/asia-pacific/malaysia-complains-vietnam-over-south-china-sea-reef-expansion-sources-say-2024-11-04/.
[17] Surya Narayan, “The Mandala: A Political Model of Southeast Asian History,” The Better Cambodia, 9 April 2025, https://thebettercambodia.com/the-mandala-a-political-model-of-southeast-asian-history/.
[18] Tyler Liggett et. al., “How the United States Can Support Allied and Partner Efforts to Counter China in the Gray Zone,” Rand, 2024, https://www.rand.org/content/dam/rand/pubs/research_reports/RRA2900/RRA2954-2/RAND_RRA2954-2.pdf#:~:text=We%20highlighted%20the%20potential%20value%20of%20presence,law%20enforcement%20responses%20to%20China%27s%20gray-zone%20aggression.
[19] “MINDEF Implements WOGOS Strategy on Pulau Banggi – Mohamed Khaled,” Bernama, 24 November 2025, https://www.bernama.com/en/news.php?id=2494440.
[20] Van Do-Tuan Anh, “Cambodia NA unanimously ratifies UNCLOS,” VOV5, 17 January 2026, https://vovworld.vn/news/cambodia-na-unanimously-ratifies-unclos-2405280.vov5.
[21] Fan Chen, “South China Sea expert warns 2026 code of conduct is ‘simply not achievable,’” South China Morning Post, 2 March 2026, https://www.scmp.com/news/china/diplomacy/article/3345137/south-china-sea-expert-warns-2026-code-conduct-simply-not-achievable.
[22] H.D.P. Envall, “South China Sea Perspectives: Japan,” Parliament of Australia Library, 7 October 2022, https://hdpenvall.com/essays/south-china-sea-perspectives-japan/.
[23] David Fields, “Cracks in the ‘Ironclad’ South Korea – U.S. Alliance,” The Diplomat, 29 January 2026, https://thediplomat.com/2026/01/cracks-in-the-ironclad-south-korea-us-alliance/.
[24] “Philippines, South Korea leaders pledge closer cooperation as geopolitical uncertainty mounts,” Reuters, 3 March 2026, https://www.reuters.com/world/asia-pacific/philippines-south-korea-leaders-pledge-closer-cooperation-geopolitical-2026-03-03/.
[25] “The EU strategy for cooperation in the Indo-Pacific,” Joint Communication to the European Parliament and the Council, 16 September 2021, https://www.eeas.europa.eu/sites/default/files/jointcommunication_2021_24_1_en.pdf.
[26] Ron J. Lienhardt, “Asymmetric Approaches Across Domains,” Marine Corps Gazette, August 2025, p. 62, https://www.mca-marines.org/wp-content/uploads/GZ-0825.pdf.
[27] Jonathan Walberg and Ethan Connell, “How the Philippines can Counter China’s South China Sea Aggression,” The Diplomat, 23 April 2025, https://thediplomat.com/2025/04/how-the-philippines-can-counter-chinas-south-china-sea-aggression/.
[28] Jon Reisher, “Cognitive Warfare and the Indo-Pacific,” Irregular Wafare Initiative, 12 January 2026, https://irregularwarfare.org/articles/cognitive-warfare-and-the-indo-pacific/.
[29] Koichiro Takagi, “The Future of China’s Cognitive Warfare: Lessons from the War in Ukraine,” War on the Rocks, 22 July 2022, https://warontherocks.com/2022/07/the-future-of-chinas-cognitive-warfare-lessons-from-the-war-in-ukraine/.
[30] James Black, “David vs. Goliath: Cost Asymmetry in Warfare,” Rand, 6 March 2025, https://www.rand.org/pubs/commentary/2025/03/david-vs-goliath-cost-asymmetry-in-warfare.html.
[31] Julian Corbett, “Some Principles of Maritime Strategy,” The Project Gutenberg eBook, https://www.gutenberg.org/files/15076/15076-h/15076-h.htm#Page_91.
[32] Yuki Tatsumi, et. al., “Economic Coercion from the People’s Republic of China,” Stimson Center, 28 August 2025, https://www.stimson.org/2025/economic-coercion-from-the-peoples-republic-of-china/.
[33] “Malaysia and France are concluding a new defence agreement to expand strategic ties, boost local industry and integrate into global defence supply chains,” The Sun, 3 March 2026, https://thesun.my/news/malaysia-news/malaysia-and-france-finalise-new-defence-cooperation-pact/#google_vignette.
[34] Dr. Ian Storey, “The United States and ASEAN-China Relations: All Quiet on the Southeast Asian Front,” U.S. Army War College Press, 1 October 2007, https://press.armywarcollege.edu/cgi/viewcontent.cgi?params=/context/monographs/article/1664/&path_info=1908.pdf.