Beijing’s Next Play for the South China Sea

In April 2025, Chinese coast guard personnel stepped onto Sandy Cay, an uninhabited sandbar in the Spratly Islands in the South China Sea, and unfurled the Chinese flag. In much of the world, this act passed almost unnoticed. But as China’s first formal, on-the-ground assertion of sovereignty over an unoccupied land feature in more than a decade, it signaled a broader shift in Beijing’s quest for control: China is again contesting disputed land features, after years in which disputes over rights at sea have been the primary source of conflict. Beijing’s targeting of unoccupied features, which is not limited to Sandy Cay, reflects an important change since its last major island-building campaign. Between late 2013 and 2015, when the bulk of that work took place, China dredged sand and coral to enlarge seven features it already occupied, later constructing military and civilian facilities on them. By extending its activities to uninhabited features, Beijing is straining a 2002 nonbinding commitment it made with the members of the Association of Southeast Asian Nations (ASEAN) not to inhabit them. Meanwhile, Beijing continues to challenge its neighbors’ exercise of sovereign rights at sea, interfering with fishing and offshore energy activity and conducting unauthorized marine surveys in their exclusive economic zones. Beijing’s methods have been shifting, too, with high-intensity incidents becoming less frequent, although clashes this month suggest that the decline may not endure. Between February 2023 and July 2024, Chinese coast guard and maritime militia vessels often used military-grade lasers and water cannons, carried out dangerous maneuvers, and rammed vessels to obstruct Philippine resupply missions, patrols, and fishing. The lull through the first half of this year may partly have reflected Manila’s decision, as chair of ASEAN, to moderate its policy of “radical transparency,” the systematic public exposure of unlawful and coercive Chinese acts at sea. The broader easing, however, likely reflected Beijing’s choice to reduce head-on confrontations, even as it advanced its claims through large-scale infrastructure projects and quieter activities such as conducting marine scientific research, symbolically asserting sovereignty over land, and placing temporary floating structures at or near disputed features. Individually, China’s quieter acts might seem inconsequential. Collectively, they could alter the strategic landscape. They complicate the calculus of coastal states, which may judge any single Chinese move to be too minor to justify a response that risks escalation. That concern weighs especially heavily as these states face the fallout from the war in the Middle East and sweeping U.S. tariffs, pressures that may force many of them to recalibrate their relationships with Beijing. China’s strategy of consolidating and normalizing control at sea and on land threatens to erode the regional order and weaken the rule of law. Its quieter measures also threaten a key element of U.S. regional strategy. Washington has relied on exposing Beijing’s unlawful and coercive conduct to rally allies and partners behind efforts to uphold the law of the sea and sustain U.S. regional influence. If allies and partners grow less willing or able to push back against China’s advances, that strategy will falter. DEFIANCE AT SEA The contest in the South China Sea spans decades. Under the UN Convention on the Law of the Sea, a naturally formed area of land that remains above water at high tide is an island and is entitled to a territorial sea extending up to 12 nautical miles. If it can sustain human habitation or economic life of its own, it may also generate an exclusive economic zone extending up to 200 nautical miles; rocks that cannot do so may generate a territorial sea but not an exclusive economic zone. High-tide features can be subject to independent sovereignty claims even if they are located in another country’s maritime zones. But low-tide elevations—features only exposed at low tide—and fully submerged features lying beyond a territorial sea cannot be claimed as sovereign territory; if they lie within the exclusive economic zone or continental shelf of a coastal state, that state enjoys sovereign rights and jurisdiction over them. Brunei, China, Malaysia, the Philippines, Taiwan, and Vietnam each claim some or all of the features in the South China Sea. Together with Indonesia, these claimants also assert sovereign rights and jurisdiction in their exclusive economic zones, which overlap with China’s maritime claims. (Jakarta denies it has a dispute with China.) China, the United States, and other naval powers remain at odds over passage rights and freedoms of the seas. Ten years ago, a tribunal in The Hague handed the Philippines a sweeping legal victory. Convened to hear a case the Philippines brought under the UN Convention on the Law of the Sea, the tribunal rejected any Chinese claim to historic rights within the “nine-dash line”—a U-shaped demarcation that encompasses much of the South China Sea but for which Beijing has never provided coordinates. It also clarified the maritime entitlements of the Spratly features, Scarborough Shoal (an atoll west of the Philippine main island of Luzon), and Reed Bank (a submerged atoll within the Philippines’ exclusive economic zone), finding that none of these features generates an exclusive economic zone. The high-tide features are at most entitled to a territorial sea. Reed Bank forms part of the Philippines’ exclusive economic zone and continental shelf. Although legally binding only on the Philippines and China, the ruling strengthened the position of other Southeast Asian coastal states by affirming that neither China’s historic rights claim nor any exclusive economic zone extending from the features the tribunal examined could override their sovereign rights in their own exclusive economic zones. The tribunal did not decide on sovereignty over contested land features because it lacked the jurisdiction to do so. China immediately rejected the decision but paused conduct most obviously inconsistent with it: interfering with its neighbors’ resource rights and driving non-Chinese fishermen from Scarborough Shoal. Once international attention waned, however, China’s transgressions began anew. Disputes over sovereign rights and jurisdiction at sea have been the primary source of conflict since. Beijing initially sought to deter coastal states from exercising their rights, most notably warning Hanoi against drilling for oil and gas in Vietnam’s exclusive economic zone in 2017 and 2018. Washington looked away. Beijing then went further, dispatching vessels into its neighbors’ exclusive economic zones to conduct seismic surveys. Beijing continues to challenge its neighbors’ exercise of sovereign rights at sea. Offshore energy sites became recurring flash points. In 2019, a Chinese survey vessel accompanied by the Chinese coast guard triggered a months-long standoff with Vietnamese coast guard and fisheries surveillance vessels at Vanguard Bank, a submerged feature, after zigzagging through Vietnam’s exclusive economic zone in a pattern consistent with surveying. For weeks in 2020, Chinese vessels shadowed the West Capella, a drillship contracted by Malaysia’s state-owned energy company. China also maintains a presence around Reed Bank, where Manila is pursuing energy development. Fishing has generated similar friction, particularly at Scarborough Shoal, despite the tribunal’s finding that fishermen from China, the Philippines, Taiwan, and Vietnam enjoy traditional fishing rights there. Encounters at sea escalated sharply starting in early 2023, particularly around Second Thomas Shoal, a low-tide elevation in the Philippine exclusive economic zone, where the tribunal had affirmed the Philippines’ sovereign rights and jurisdiction. In 1999, Manila had deliberately grounded a Philippine naval vessel, the BRP Sierra Madre, at the shoal to forestall Chinese occupation. A small contingent of Philippine marines has remained on board ever since, dependent on periodic resupply missions. Because the ship remains in commission, an armed attack on it or its personnel could invoke U.S. commitments under the 1951 U.S.-Philippine Mutual Defense Treaty. Chinese attempts to block these missions have resulted in high-intensity clashes with the Philippines, although the clashes became less frequent after Manila and Beijing reached a provisional arrangement in July 2024. As of March, Manila reported that 13 resupply and rotation missions had proceeded without “untoward incidents.” Even so, risks remain, partly because the two sides disagree about the arrangement’s scope. This month, Philippine authorities said that Chinese coast guard personnel struck a Filipino sailor with a wooden baton during a close encounter between Chinese and Philippine vessels. Philippine officials say that Beijing is making greater use of research vessels to advance its claims, citing an unauthorized Chinese survey at Reed Bank in May. China also deploys research vessels in Malaysian and Vietnamese exclusive economic zones. According to Philippine authorities, these vessels increasingly operate in its exclusive economic zone without coast guard or maritime militia escorts and typically withdraw when challenged. THE CONTEST FOR LAND While China continues to press its claims at sea, it is also renewing its focus on disputed land features, including unoccupied ones. In October 2025, China began large-scale dredging to expand Antelope Reef in the Paracel Islands, which lies roughly 215 nautical miles east of the central Vietnamese coast. In its natural state, the reef consisted of sand patches and minor coral cays above water at high tide. Before major dredging, it already hosted a small Chinese outpost. The latest work—China’s first significant island-building campaign in about a decade—is much more extensive. Satellite imagery suggests the reef is on track to become China’s largest military outpost in the South China Sea. According to the Center for Strategic and International Studies’ Asia Maritime Transparency Initiative, it could accommodate a runway, harbor, missile facilities, underground storage, and surveillance and electronic warfare systems. This would extend Chinese sensing capabilities closer to Vietnam, add capacity and redundancy for China’s naval and air operations, and allow Beijing to expand its civilian presence in the Paracels. China’s recent activities on land extend beyond large-scale reclamation and infrastructure construction. The Sandy Cay landing involved only a Chinese flag held up for the cameras. But Beijing’s actions there have strategic significance: the sandbar lies barely two nautical miles from the Philippine-occupied Thitu Island, so the two land features’ 12-nautical-mile territorial seas overlap almost entirely. By staking a claim to Sandy Cay, China narrows the Philippines’ operational space around a major Philippine outpost and lays the groundwork for future legal challenges. Beijing could, for example, object to Philippine patrols and other activities around Thitu Island on the basis of its claim to waters around Sandy Cay. China has also sought to consolidate its administrative control at Scarborough Shoal, access to which it has controlled since 2012 without occupying the feature. In September 2025, Beijing approved the creation of a national nature reserve there. This seemingly innocuous measure asserted China’s jurisdiction and allowed Beijing to present fishing restrictions as law enforcement against environmental harm. At the end of May, China deployed a floating structure at the shoal that Philippine officials said was manned. Beijing claimed it was for research. After Manila demanded its removal, a Chinese research vessel towed it away. This month, Chinese coast guard vessels confronted Philippine government vessels delivering fuel and food to Filipino fishermen at the shoal. According to Philippine officials, Chinese ships fired a water cannon and conducted a dangerous maneuver against two Philippine vessels. The Philippines has been at the forefront of resistance to Chinese pressure. China maintains it is free to act on features over which it claims sovereignty. Because sovereignty in these cases is unresolved—unlike sovereign rights and jurisdiction over water, which the Hague tribunal clarified—most of Beijing’s moves on land fall into a legal gray zone. (Some might breach environmental obligations under the UN Convention on the Law of the Sea.) This leaves governments fewer clear legal grounds to challenge China’s activities on land than they have to challenge its activities at sea. For almost a quarter of a century, claimant states fortified features they already occupied but stopped short of inhabiting unoccupied ones—conduct that China and ASEAN members expressly singled out for “self-restraint” in the 2002 Declaration on the Conduct of Parties in the South China Sea, a nonbinding political agreement. But Beijing’s recent activities, designed to normalize China’s presence and edge toward occupation, are undermining that norm. These developments carry real risks. Philippine officials are rightly concerned that Beijing seeks a sustained presence on unoccupied land features to pave the way for eventual occupation. If China were to occupy and militarize Scarborough Shoal, that base, together with bases in the Paracels and Spratlys, would strengthen Beijing’s ability to monitor maritime and air activity and project power across the sea. Such an outpost would also extend Chinese sensor and strike capabilities closer to the Luzon Strait, a strategic waterway between the Philippines and Taiwan, and place Manila well within striking range. China’s actions could also prompt other claimants to take similar steps, potentially leading to confrontations with Beijing and with one another. All this could further weaken the prospects for a Code of Conduct for the South China Sea, a more detailed and potentially binding set of rules that China and ASEAN members have pursued for decades. Even if a final deal is unlikely, the polite fiction that the parties are near one has afforded some stability. THE COST OF RESISTANCE China’s moves are difficult to counter. Large-scale island-building and violent clashes at sea command international attention and demand a response. A flag raising or a temporary floating structure on a small, obscure feature is easily overlooked or dismissed. The Sandy Cay episode elicited only a minor response from Washington: the White House merely said that reports of a Chinese seizure were “deeply concerning if true.” Even when such acts are detected, governments may conclude that they are too minor to warrant a response, or that responding risks provoking escalation with China. The uncertain legality of China’s acts may further dissuade them from reacting. Beijing may thus alter the status quo through actions carefully chosen to avoid the pushback that has followed its more dramatic or clearly unlawful conduct at sea. So far, the Philippines has been at the forefront of resistance to Chinese pressure. Recently describing itself as the “guardian of the freedom of the seas,” Manila has committed to safeguarding the legal and physical infrastructure that enables the world “to sail, to trade, and to prosper.” It has deepened its network of security partnerships, including with the United States. U.S. Secretary of Defense Pete Hegseth visited Manila soon after his appointment, and the Trump administration exempted roughly $336 million earmarked for modernizing the Philippines’ military from a broader freeze on foreign aid. Late last year, the U.S. Congress enacted legislation authorizing up to $2.5 billion in grants through 2030 for Manila to acquire U.S.-made defense equipment, and in June Washington approved a $60 million grant program to modernize the Philippines’ energy sector and support economic development. Military assistance can boost Philippine surveillance and operational capacity and help sustain patrols and resupply missions, while energy aid can address vulnerabilities Beijing could exploit to limit Manila’s ability to push back. Beyond the United States, the Philippines has expanded joint maritime patrols with Australia and increased defense cooperation with Japan. Manila and Tokyo have also recently announced negotiations to delimit their overlapping exclusive economic zones, as required under the UN Convention on the Law of the Sea. The area in question overlaps with an exclusive economic zone extending eastward from Taiwan. Beijing denounced the talks and dispatched coast guard vessels on what it called “law enforcement patrols” to reinforce its claim to sovereignty over Taiwan and the maritime rights flowing from it. Even negotiations undertaken to fulfill international legal obligations can trigger Chinese countermeasures and raise the costs of cooperation for countries in the region. UNDER PRESSURE Southeast Asian states determined to curb China’s worst impulses may nonetheless find it necessary to adopt a more pragmatic approach to South China Sea disputes. The region’s stability and development have depended in part on maintaining workable relations with China. Severe external shocks, foremost among them the Iran war and U.S. tariffs, and domestic political strains could make some kind of rapprochement with Beijing increasingly difficult to avoid. Even the Philippines may seek accommodation. Within Southeast Asia, it is among the hardest hit by the Iran war’s economic fallout. It sources roughly 98 percent of its crude oil imports from the Middle East. Of the three million Southeast Asians who live or work in that region, an estimated 2.4 million are Filipinos. Disruptions to energy supplies and uncertainty over remittance flows are compounding the effects of U.S. tariffs, and President Ferdinand Marcos, Jr., faces public pressure after corruption-related failures in flood-control infrastructure contributed to hundreds of deaths in 2025. Early in his six-year term, which began in 2022, Marcos told Beijing that maritime disputes were not the “sum” of the bilateral relationship. In March, he said that the Iran war could provide the “impetus” for an agreement with Beijing on oil and gas development. Days later, his government restarted high-level talks with China on energy cooperation and maritime de-escalation. Countering China’s strategy requires more than conventional naval power. Still, energy cooperation between China and the Philippines remains fraught. Previous talks in 2018 and 2019 collapsed over Philippine constitutional constraints and China’s refusal to acknowledge Philippine sovereign rights in any final agreement. Today, the Philippine defense establishment and the public remain deeply suspicious of Beijing, and any perception that Marcos is striking a deal with China could further erode his political standing. Continued Chinese operations on and around Philippine-claimed land features or within the Philippine exclusive economic zone could quickly derail negotiations. Yet if Manila and Beijing can overcome those complications and there is a sustained reduction in head-on confrontations—something the clashes in late July show is far from assured—a quiet rapprochement could emerge. It need not entail abandoning Philippine claims. In practice, Manila might make greater efforts to avoid clashes at sea, rely less on public exposure of Chinese actions, and place greater emphasis on stabilizing relations with Beijing. A Philippine adjustment along these lines could make it harder for the United States and other countries to confront expansive Chinese claims. The Philippines’ legal challenge and highly visible clashes with China have lent force to Washington’s argument that Beijing flouts international law and that there is regional demand for U.S. support in countering its actions. If Manila steps back, Washington may find it harder to mobilize coordinated responses to Beijing’s actions in the South China Sea and beyond. HOLDING THE LINE After a decade in which Chinese pressure focused on encroaching on other countries’ rights at sea, Beijing is again extending the contest to land, including unoccupied features. In both domains, China’s aim is the same: the steady accumulation of advantage rather than a single decisive victory. By combining quieter tactics with more confrontational moves at sea and operating, often unnoticed, within legal gray zones on land, Beijing is betting that it can gradually normalize its control across the South China Sea. Countering this strategy requires more than conventional naval power. U.S. naval strength remains important for deterrence and for responding if armed force is used, but the U.S. Coast Guard is better suited to gray-zone encounters: it can patrol alongside regional coast guards in a law enforcement capacity, and it can respond to China’s coast guard and maritime militia with less risk of escalation than a naval deployment. Continuing to expand the Coast Guard’s regional role would help allies and partners more effectively monitor and document Chinese activities. Washington should respond consistently and promptly to both China’s large-scale construction and its quieter efforts to assert sovereignty. It joined Manila in rejecting Beijing’s declaration of a national nature reserve at Scarborough Shoal, but it expressed only vague concern over the Sandy Cay landing and made no public response to the Antelope Reef reclamation. Washington should reiterate that Beijing must honor its 2002 commitment not to inhabit currently uninhabited disputed features. It should also emphasize relevant legal principles and norms: that claimants should refrain from making irreversible changes to features, which aggravate disputes and complicate any future settlement; that reclamation cannot alter a feature’s legal status or create new maritime entitlements; and that acts of physical control, construction, flag raising, and unilateral administration generally will not strengthen a claimant’s legal position. None of this requires Washington to abandon its long-standing neutrality on competing sovereignty claims. Where appropriate, Washington should reinforce its public statements with targeted economic measures and support for claimants pursuing legal action against unlawful Chinese conduct. Such measures may not significantly weaken entrenched Chinese control over features such as Antelope Reef, but they can impede the normalization of China’s activities, raise the costs to Beijing of further consolidating control, and deter similar moves elsewhere. A particular priority is preventing Beijing from reclaiming and establishing a permanent outpost at Scarborough Shoal. Washington and Manila should agree in advance to a graduated diplomatic, economic, and operational response to any such attempt. These efforts depend on Washington’s credibility. Countries in the region must trust the United States to act dependably, to counter China without needless escalation, and to observe the international law it invokes. Washington must deepen its economic and diplomatic engagement across Southeast Asia and correct course on policies in the region and beyond that constrain its partners’ ability to resist Beijing. Above all, the United States and its allies and partners must see China’s advances at sea and on land for what they are and respond before the cumulative effects of individually minor acts harden into a new regional order. 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