The South China Sea as the Enabling Battlespace of Maritime Control
Control of the South China Sea determines strategic leverage in the Indo-Pacific, driving sustained great-power rivalry, grey-zone coercion, and complex hedging by Taiwan, the Philippines and ASEAN amid shifting US-China power balances.
The South China Sea constitutes the central enabling battlespace for maritime control in the Indo-Pacific. Its geography and strategic significance make sustained presence essential for China, the United States, Taiwan and the Philippines. Control over these waters allows states to secure supply lines, extend operational reach and project power across the wider region. In the event of a China-Taiwan crisis, dominance in the South China Sea could facilitate Taiwan’s isolation and constrain US and Philippine intervention. Conversely, sustained presence and surveillance by the United States and the Philippines can complicate Chinese objectives and reinforce deterrence.
The region also illustrates broader strategic dynamics. Rising and established powers compete over influence, control of maritime rules and the structures of regional security. These dynamics mirror a wider pattern in international politics, in which challenges to an existing order generate instability as emerging powers seek to reshape regional arrangements.
Transitions of Power and Competing Orders
Power transition theory, as introduced by Organski (1958, cited in CIRIS, n.d. ), posits that instability increases as a rising power approaches parity with a dominant state, especially when the challenger seeks to revise and is dissatisfied with the existing international order (CIRIS, n.d.). China’s rapid economic growth and expanding maritime capabilities place it in a position to challenge elements of the existing order. Rather than pursuing outright confrontation, Beijing has adopted a gradual strategy, relying on incremental actions to expand control while avoiding open warfare.
China does not reject international order; it opposes a US-dominated system and seeks to reform global governance with the principles of fairness and justice, a goal made more achievable by the Trump administration’s retrenchment from global leadership (Council on Foreign Relations, n.d.). Maritime control in adjacent seas is central to this revisionist strategy. China’s naval expansion underpins this strategy: it now operates the world’s largest navy by hull count (Srivastava, 2025) and has transformed its coast guard into a paramilitary force tasked with enforcing sovereignty claims. Control of the South China Sea reduces vulnerability along China’s maritime periphery and limits US alliance leverage, helping to explain why Beijing is willing to accept reputational costs and diplomatic friction in exchange for practical control over the region.
China’s expansion occurs in the context of a relative decline in US influence across the region. Debates over American decline focus on relative rather than absolute power; the US retains unmatched global capabilities, yet its regional dominance has eroded. Alliance burdens, domestic polarisation and competing strategic theatres increasingly limit its freedom of action. Hegemonic decline stems not only from shifts in relative power but also from internal political decay, reframing US leadership debates from whether it can lead to whether it can agree with itself enough to lead (Kanji, 2025), p.5).
Declining powers struggle not because they lack material resources, but because domestic polarisation can undermine the credibility and strategic utility needed to translate power into effective global leadership (Kanji, 2025, pp.27-28). In maritime Asia, this dynamic leads to selective American engagement. Freedom of navigation operations signal commitment while avoiding permanent deployments near contested features which gives China room to act incrementally. Allies perceive reassurance, but adversaries see restraint, raising the risk of miscalculation and highlighting that such limited actions are insufficient for exercising effective hegemonic leadership.
Structural realism helps to explain why the South China Sea remains unstable. In an anarchic international system, states seek security through self-help, and one state’s defensive measures can appear threatening to others (Taliaferro, 1999; Kanji, 2025, pp.25-28). Chinese patrols presented as law enforcement are perceived as coercive by neighbours, while US presence framed as stabilising appears threatening to China. Overlapping claims, diverging interests, and constant interaction amplify these misperceptions, producing a persistent security dilemma.
Within this environment, states continuously adjust their behaviour in response to perceived threats, reinforcing cycles of caution, signalling and competition. To advance their interests while avoiding open military confrontation, they often pursue strategies commonly described as grey-zone operations. China exemplifies this approach. Coast guard vessels, maritime militia, and administrative measures replace naval battle; law substitutes for force, and presence substitutes for conquest (Mazarr, 2015). This approach exploits asymmetries in escalation tolerance.
The Philippines experiences this directly. Its legal victory in 2016 clarified maritime rights but did not alter behaviour at sea, effectively shifting contestation from legal forums back to power politics. China’s maritime assertions are seen as coercive by Southeast Asian states, while US freedom of navigation operations are viewed as provocative by China. The concentration of contested features, major shipping lanes, and strategic chokepoints intensifies these misperceptions, sustaining the underlying security dilemma. Recent incidents illustrate this pattern clearly. Philippine and Chinese vessels have collided, and Filipino fishermen have reported harassment near Sabina Shoal, prompting formal diplomatic protests (Associated Press, 2025). Philippine officials condemn these actions as dangerous and contrary to international norms, while China frames them as lawful measures to protect its sovereignty. Taken together, these episodes demonstrate that tensions in the South China Sea stem from sustained strategic competition rather than isolated errors or miscalculations.
Taiwan and Strategic Exposure
Taiwan’s security is tightly linked to control of the South China Sea and adjacent waters, which function as the enabling battlespace for regional power projection. The People’s Republic of China possesses the capability to impose a maritime blockade, restricting commercial shipping and effectively sealing Taiwan’s ports while remaining below the threshold of open warfare (Atlantic Council, 2023). Given Taiwan’s heavy dependence on maritime trade for economic survival, even a non-kinetic blockade would directly affect reinforcement timelines and the ability of allies to intervene. Control of these surrounding waters therefore shapes both operational depth and strategic reach. This reinforces the need for Taiwan to incorporate the South China Sea into its broader defence planning, treating it as part of an interconnected maritime environment rather than a separate or secondary theatre. Such an approach reflects the reality that pressures applied beyond Taiwan’s immediate coastline can have decisive effects on its security and resilience.
The Philippines and the Small State Energy
The Philippines faces structural constraints common to smaller powers operating in asymmetrical systems (Misalucha-Willoughby & Medillo, 2020). It cannot match China militarily but must safeguard its sovereign rights and economic interests in contested waters. Research indicates that survival under systemic competition depends less on direct military confrontation and more on a combination of alliance-building, legal strategy and the internationalisation of state disputes. The Philippines adopts diverse policy options to produce bilateral offsetting effects in a context of high uncertainty and highly correlated interests (Han, Jiang & Peng, 2023). Manila relies on the 2016 arbitral ruling under the United Nations Convention on the Law of the Sea to challenge expansive Chinese claims. The Philippine government engages in bilateral and multilateral relations with like-minded nations and adopts transparency initiatives that publicise incidents involving Chinese actions against Filipino fishermen and the destruction of their vessels (Ibarra & Arugay, 2024). Collectively, these measures enhance the legitimacy of Philippine claims and shape global opinion, providing diplomatic leverage without escalating to armed conflict.
ASEAN and Collective Institutional Strategy
ASEAN’s institutional role in the South China Sea remains central but constrained by its consensus-based decision making and its principles of non-interference and neutrality which limit its capacity to manage sustained great-power competition. While the bloc’s informal institutional structures have facilitated dialogue, they have struggled to produce decisive collective security responses to repeated Chinese coercive actions at sea (Koga, 2018).
ASEAN has sought to embed discussions on the South China Sea within broader regional forums such as the East Asia Summit, in order to diffuse tensions and widen diplomatic engagement. However, these efforts reflect a strategy of hedging and incremental adaptation rather than robust balancing. This strategy aims to balance Chinese influence with US engagement and other external partners while avoiding overt strategic polarisation.
For the Philippines, three interlinked priorities emerge from this contested maritime environment.
First, strengthening maritime cooperation and domain awareness through coordinated operational frameworks. Analysts emphasise the importance of united maritime responses that integrate the Philippine Navy, Coast Guard, and fisheries resources to build credible presence, enhance surveillance, and deter coercive actions at sea (Walberg & Connell, 2025).
Second, ASEAN should deepen its collective security capacity beyond consensus building around a code of conduct by developing mechanisms for real-time information sharing, confidence-building and coordinated patrols. ASEAN’s role in advocating for a substantive and enforceable code of conduct reflects an effort to translate institutional rhetoric into tangible measures that reduce the risk of miscalculation and manage tensions among claimants. Crucially, such mechanisms must incorporate the voices of smaller claimant states rather than defer solely to great-power diplomacy.
Third, strategic hedging and diversified partnerships remain essential. The Philippines’ efforts to expand cooperation with the United States, Japan, Australia and other like-minded partners through RAA, help distribute risk, build interoperability and signal resolve without excessive dependence on any single partner (Shidore, 2025). Strategic hedging supports broader regional resilience, reinforces shared norms of maritime conduct, and enhances collective capacity to resist coercive pressures in the enabling battlespace of the South China Sea.
Conclusion
Control of the South China Sea is the decisive factor shaping regional security and political outcomes. Operational success depends on maintaining a credible presence, effective surveillance, and coordinated maritime responses to deter coercion and protect sovereign interests. China’s use of incremental pressure, including coast guard and maritime militia demonstrates how influence can be exerted below the threshold of war, while Philippine and allied actions show how persistence and visibility preserve deterrence. Taiwan’s security, the Philippines’ strategic hedging, and ASEAN’s institutional limitations all illustrate that maritime control shapes reinforcement, access and strategic leverage across the contested theatre. Preventing conflict requires sustained presence, clear coordination, and calibrated responses by all claimants and their allies. Legal frameworks, alliances and institutional arrangements must be treated not as abstract principles but as practical instruments for managing disputes, maintaining influence and reducing risk. Accordingly, strategy and doctrine must focus on leveraging the South China Sea as the enabling battlespace to generate operational and political effects.
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