South China Sea

The South China Sea is a 3.5 million square kilometer (1.4 million square mile) body of water bounded by China, Taiwan, the Philippines, Malaysia, Brunei, Indonesia, and Vietnam. Through its waters passes approximately $5.3 trillion in trade annually—roughly one-third of global maritime commerce. Beneath its seabed lie potentially vast oil and gas reserves, estimated at 11 billion barrels of oil and 190 trillion cubic feet of natural gas in proven and probable deposits. Its fisheries provide protein for hundreds of millions of people and employment for millions of fishermen.

And across its waves, the united-states and China are engaged in a strategic competition that may define the century. The South China Sea sits at the intersection of the three great challenges facing the existing international order: the rise of China, the durability of American alliances, and the enforceability of international law.

Geographic Significance¶

Location¶

The South China Sea connects the Indian and Pacific Oceans, serving as the maritime crossroads of Asia. Its strategic position makes it one of the world’s most important waterways:

• To the southwest: The strait-of-malacca (through which passes approximately 25% of global oil trade and 25% of global maritime trade) and the Indian Ocean
• To the northeast: The taiwan-strait and the Western Pacific, home to Japan, South Korea, and American bases in Guam
• To the south: The Indonesian archipelago and Australia
• To the northwest: China’s coast and industrial heartland—the Pearl River Delta (including Shenzhen, Guangzhou, and Hong Kong) hosts manufacturing capacity serving the entire world

For China, the South China Sea is the gateway to the world. Approximately 40% of Chinese trade passes through these waters. sea-power theorists like alfred-mahan would recognize the sea as a vital maritime crossroads whose control confers enormous strategic advantage. For the United States and its allies, it is a critical link in the chain connecting the Pacific to the Indian Ocean—and a barrier to Chinese regional hegemony.

The First Island Chain¶

The South China Sea’s significance is amplified by its position relative to the first-island-chain—the string of islands from Japan through Taiwan, the Philippines, and Indonesia that separates China from the open Pacific:

• This chain provides the United States and its allies with bases and geographic positions that can contain Chinese naval expansion
• Conversely, it represents to China a barrier that must be breached for China to become a true Pacific power
• Control of the South China Sea would allow China to operate inside the first island chain and project power beyond it

Islands and Features¶

The sea contains over 250 small islands, reefs, rocks, shoals, and sandbars grouped into three main archipelagos:

• Paracel Islands (Xisha in Chinese, Hoang Sa in Vietnamese): Located approximately 200 miles southeast of Hainan Island, this group of 130+ features has been controlled by China since 1974, when the PLA Navy seized them from South Vietnam. The Paracels host military installations including an airstrip on Woody Island (2.4 km runway), radar facilities, and missile systems. Vietnam and Taiwan also claim the islands.

• Spratly Islands (Nansha in Chinese, Truong Sa in Vietnamese): The largest and most contested group, comprising approximately 100 islands, reefs, and banks spread across 425,000 square kilometers. Six governments occupy features: China (7 artificial islands), Taiwan (1 island), Vietnam (21 features), the Philippines (9 features), Malaysia (5 features), and Brunei (none, but claims an EEZ overlapping the area). The Spratlys lie astride major shipping lanes and atop potential hydrocarbon deposits.

• Scarborough Shoal (Huangyan in Chinese, Bajo de Masinloc in Filipino): A ring-shaped reef 120 miles west of the Philippine island of Luzon, inside the Philippine EEZ. China effectively seized control in 2012 following a standoff with Philippine vessels. The shoal provides rich fishing grounds and, potentially, a platform for military installations.

Many features are barely above water at high tide—some are submerged entirely at high tide—yet they have become objects of intense competition. Under UNCLOS, only islands capable of sustaining human habitation generate full EEZ rights; rocks and low-tide elevations generate lesser or no rights. The legal status of each feature carries enormous economic implications.

Competing Claims¶

The Nine-Dash Line¶

China claims sovereignty over most of the South China Sea based on historical presence, demarcated by a vague “nine-dash line” that encompasses approximately 90% of the sea. This claim:

• Has no clear legal basis under international law
• Was rejected by a 2016 Permanent Court of Arbitration ruling
• Overlaps with the exclusive economic zones of neighboring states
• Is enforced by an increasingly powerful Chinese coast guard and navy

Beijing has refused to accept the arbitration ruling, calling it “null and void.”

Southeast Asian Claims¶

The littoral states assert claims based on the UN Convention on the Law of the Sea (UNCLOS):

• Vietnam: Claims the Paracels and Spratlys based on historical sovereignty and UNCLOS
• Philippines: Claims features within its exclusive economic zone
• Malaysia: Claims features on its continental shelf
• Brunei: Claims an exclusive economic zone overlapping Chinese claims
• Indonesia: Does not claim islands but asserts EEZ rights that China contests

Taiwan¶

Taiwan (ROC) maintains the same historical claims as mainland China—a legacy of the pre-1949 Republic of China government. Taiwan occupies Itu Aba (Taiping Island), the largest naturally occurring island in the Spratlys.

Strategic Importance¶

Trade Routes¶

The South China Sea’s economic importance is immense—arguably unparalleled among the world’s waterways:

• $5.3 trillion in trade passes through annually (approximately 30% of global maritime commerce), of which $1.2 trillion involves the United States
• Over 100,000 vessels transit the sea each year—nearly 300 per day
• 60% of maritime trade for Japan, South Korea, and Taiwan passes through these waters
• 80% of Chinese oil imports cross the South China Sea, primarily from the Middle East via the strait-of-malacca
• Critical supply chains: Electronics components, semiconductors, consumer goods, and raw materials crisscross the sea daily

A major disruption—whether from conflict, blockade, or accident—would devastate global supply chains within days. Container shipping rates would spike; automobile factories would halt for lack of parts; electronics shortages would ripple through every economy. The economic consequences would dwarf those of the 2021 Suez Canal blockage.

Resources¶

The seabed and waters contain significant resources that add economic stakes to strategic rivalry:

• Oil and gas: The U.S. Energy Information Administration estimates proven and probable reserves of 11 billion barrels of oil and 190 trillion cubic feet of natural gas—modest by global standards but significant for regional economies. Chinese estimates are far higher (up to 130 billion barrels of oil), though these are disputed. Exploration remains limited due to overlapping claims; joint development has proven politically impossible.

• Fisheries: The South China Sea provides approximately 12% of global fish catch—the primary protein source for hundreds of millions of people. Fishing provides livelihoods for millions of fishermen in Vietnam, the Philippines, Indonesia, and China. Overfishing has depleted stocks by 70-95% since the 1950s, intensifying competition for remaining resources.

• Seabed minerals: Polymetallic nodules and other minerals may become economically viable as technology improves and land-based deposits are depleted.

Military Geography¶

For China, the South China Sea is a defensive buffer and a platform for power projection:

• Submarine bastion: The deep waters south of Hainan Island (depths exceeding 5,000 meters in places) allow Chinese nuclear-armed submarines to operate with reduced detection risk. China’s Jin-class ballistic missile submarines, based at Yulin Naval Base on Hainan, could strike the continental United States with JL-2 missiles if they can reach deep water undetected.

• Strategic depth: Distance from the Chinese coast provides warning time against attack and complicates American military planning. Control of the South China Sea would push the effective American defensive perimeter from the first island chain back hundreds of miles.

• A2/AD zone: Chinese missiles, aircraft, and naval forces deployed in the South China Sea create an “anti-access/area denial” environment that raises the costs and risks of American intervention. The artificial islands provide unsinkable platforms for radar, missiles, and aircraft.

For the united-states, freedom of navigation in the South China Sea:

• Enables power projection throughout Asia, supporting treaty allies in Japan, South Korea, the Philippines, and Taiwan
• Reassures allies that American security commitments remain credible
• Prevents Chinese regional hegemony that could dominate the economies and security policies of Southeast Asia
• Upholds international law, specifically the UNCLOS principle that maritime navigation is free beyond territorial waters

China’s Strategy¶

Island Building Campaign (2013-2017)¶

Beginning in late 2013, China undertook the largest artificial island construction project in history, transforming submerged reefs into military-capable islands:

• Scale: China created approximately 3,200 acres (13 square kilometers) of new land in the Spratly Islands alone—more than all other claimants combined have built in the past four decades
• Method: Dredging vessels pumped sand and crushed coral onto submerged reefs, then compacted and surfaced the new land. The process destroyed coral ecosystems and drew international condemnation.
• Speed: Most construction occurred between 2014 and 2017, with some features going from bare reef to functioning military base in 18-24 months

The seven artificial islands in the Spratlys now host substantial military infrastructure:

These installations effectively create an air and sea control zone covering much of the southern South China Sea. In 2018, China deployed HQ-9 surface-to-air missiles and YJ-12B anti-ship cruise missiles to three islands—a significant escalation that Xi Jinping had previously promised not to undertake.

Coast Guard Assertiveness¶

China has deployed the world’s largest coast guard—approximately 130 large vessels (over 500 tons) plus hundreds of smaller craft—to enforce its claims:

• Blocking Philippine resupply missions: Chinese coast guard vessels have repeatedly used water cannons, lasers, and physical blocking to prevent the Philippines from resupplying its outpost on Second Thomas Shoal (a rusting ship intentionally grounded in 1999)
• Confronting Vietnamese fishing vessels: Coast guard and maritime militia vessels have harassed, rammed, and sunk Vietnamese fishing boats in disputed waters
• Shadowing American naval operations: Every U.S. freedom of navigation operation draws close escort from Chinese coast guard and navy vessels
• 2021 Coast Guard Law: China passed legislation authorizing coast guard use of weapons against foreign vessels in waters China claims—a significant legal escalation

The coast guard operates in a gray zone—less escalatory than military action but effectively asserting control while avoiding triggers that might justify military response.

Salami Tactics¶

China has pursued incremental gains that individually seem too small to warrant strong response:

• Scarborough Shoal (2012): Following a standoff with Philippine vessels, China established permanent presence at this feature 120 miles from Luzon. The Philippines could not escalate; the U.S. did not intervene; China gained control.
• Oil rig deployment (2014): China deployed the Haiyang Shiyou 981 oil rig in waters Vietnam claims, triggering protests and riots but no reversal
• Gradual militarization: Each new radar installation, each runway extension, each missile deployment represented a small step that did not trigger intervention but cumulatively transformed the strategic environment

This approach—sometimes called “cabbage strategy” (wrapping disputed features in successive layers of fishing boats, coast guard, and navy)—has proven remarkably effective. China has expanded its effective control throughout the sea while avoiding the direct confrontation that might unite opposition.

American Response¶

Freedom of Navigation Operations (FONOPs)¶

The U.S. Navy conducts regular Freedom of Navigation Operations to challenge Chinese claims and assert that international law governs these waters:

• Frequency: The U.S. has conducted approximately 10+ FONOPs per year since 2015, up from sporadic operations in earlier years
• Operations: Warships transit within 12 nautical miles of features China claims, challenging the assertion that these waters are Chinese territorial seas. Specific operations have challenged straight baseline claims, excessive maritime zone claims, and restrictions on military activities in EEZs.
• China’s response: Each FONOP draws Chinese protest and close shadowing by PLA Navy and coast guard vessels. China condemns the operations as provocative violations of sovereignty; the U.S. considers them essential demonstrations that Chinese claims do not alter international law.

The legal signaling matters: if no one challenges excessive claims, they may become accepted through acquiescence. FONOPs assert that the U.S. (and the international community) does not recognize Chinese sovereignty over the South China Sea.

Alliance and Partnership Building¶

The United States has strengthened relationships with regional states to build a coalition capable of resisting Chinese pressure:

• Philippines: Despite fluctuations (the Duterte administration pursued accommodation with China), the alliance has strengthened under President Marcos Jr. The U.S. gained access to four additional bases under the Enhanced Defense Cooperation Agreement (2023), including sites facing Taiwan and the South China Sea. The U.S. has explicitly stated that the 1951 Mutual Defense Treaty covers Philippine vessels in the South China Sea.

• Vietnam: The former adversary has drawn steadily closer to Washington. The 2023 upgrade to a Comprehensive Strategic Partnership placed Vietnam at the highest level of diplomatic relations. The U.S. has provided coast guard cutters and maritime domain awareness support; Vietnam permits U.S. carrier port calls.

• Quadrilateral Security Dialogue: The “Quad” (U.S., Japan, Australia, India) has evolved from occasional consultations to regular summits and extensive maritime cooperation. While not focused exclusively on the South China Sea, the Quad represents the nucleus of a potential balancing coalition.

• AUKUS: The 2021 Australia-UK-US agreement to provide Australia with nuclear-powered submarines signals long-term commitment to the Indo-Pacific and will eventually enhance allied capability in the South China Sea.

Strategic Ambiguity¶

American policy on South China Sea disputes combines clarity and ambiguity:

• Clear positions: The U.S. takes no position on sovereignty over specific features but has clearly stated that China’s nine-dash line claim is unlawful, that the 2016 arbitration ruling is final, and that freedom of navigation must be preserved.
• Ambiguous commitments: The U.S. defense treaty with the Philippines covers armed attacks—but its application to gray zone confrontations, disputed features, or attacks by coast guard rather than military forces remains unclear. Would the U.S. fight to defend Second Thomas Shoal? Scarborough Shoal?

This ambiguity provides flexibility—the U.S. is not committed to automatic escalation—but may also create uncertainty that China exploits. If Beijing believes the U.S. won’t actually fight over reefs and shoals, the deterrent effect of American commitments weakens.

Regional Responses¶

ASEAN¶

The Association of Southeast Asian Nations has struggled to present a unified response:

• China’s economic leverage divides members
• Cambodia and Laos often block anti-China consensus
• Negotiations on a Code of Conduct have dragged for decades
• Individual states pursue bilateral deals with Beijing

ASEAN unity remains elusive.

Individual Strategies¶

Southeast Asian states have adopted varied approaches:

• Philippines: Oscillated between confrontation (Aquino) and accommodation (Duterte) before returning to closer US ties
• Vietnam: Maintained firm resistance while developing military capabilities
• Malaysia: Pursued quiet diplomacy while building its own presence
• Indonesia: Denied having disputes with China while strengthening defenses

No state has found an effective counter to Chinese pressure.

Scenarios¶

Confrontation¶

Risks of military confrontation exist and may be increasing:

• Accidents or incidents: The density of military operations creates constant collision risk. In 2001, a Chinese fighter collided with a U.S. EP-3 surveillance aircraft, forcing an emergency landing on Hainan. Similar incidents could escalate, particularly if vessels or aircraft are damaged or personnel are killed.

• Second Thomas Shoal crisis: The deteriorating situation at the Philippine outpost on Second Thomas Shoal (the BRP Sierra Madre) creates ongoing risk. Chinese forces have used water cannons, lasers, and blocking maneuvers against Philippine resupply missions. A sinking, boarding, or casualties could trigger the U.S. mutual defense treaty.

• Taiwan connection: A conflict over Taiwan would immediately involve the South China Sea. Chinese forces would seek to control the sea to prevent American reinforcement via the Philippine Sea; American forces would need to operate through South China Sea waters to reach Taiwan.

• Gray zone escalation: The accumulation of coast guard confrontations could eventually produce a triggering incident. At some point, water cannons and lasers may prove insufficient to deter Philippine resupply, and China must decide whether to escalate or back down.

The region’s strategic importance means that conflict here could escalate rapidly to general war between the United States and China—with nuclear-armed great powers facing off directly.

Accommodation¶

Alternatively, the region could evolve toward Chinese dominance:

• American withdrawal: Domestic political pressure, resource constraints, or priorities elsewhere could lead to reduced American commitment. If allies doubt American resolve, they may accommodate Chinese preferences.
• Regional bandwagoning: Southeast Asian states, dependent on Chinese trade and unable to match Chinese power, could accept de facto Chinese dominance—a form of “Finlandization” that preserves formal independence while deferring to Beijing on strategic matters.
• International law erosion: If China successfully establishes control despite the 2016 ruling, the principle that international law constrains great powers would be significantly weakened.

Managed Competition¶

The most likely near-term outcome is continued competition:

• Ongoing pressure and resistance: China continues to press for advantage; the U.S. and allies continue to resist through FONOPs, alliance building, and diplomatic pressure.
• No decisive victory: Neither side achieves the control it seeks. China cannot expel American forces from the region; the U.S. cannot reverse Chinese island building or coast guard assertiveness.
• Periodic crises: Incidents at Second Thomas Shoal, air intercept mishaps, or coast guard confrontations generate recurring tensions that are managed short of war.
• Gradual erosion: The rules-based order slowly weakens as Chinese effective control expands and international law proves unenforceable against a determined great power.

This scenario could persist for decades, much as the Cold War maintained extended competition without resolution.

Conclusion¶

The South China Sea is where the fundamental questions of 21st-century geopolitics are being answered:

• Will China achieve regional hegemony?
• Will the United States maintain its Asian commitments?
• Can international law constrain great power behavior?
• Will the nations of Southeast Asia retain genuine sovereignty?

The artificial islands rising from once-submerged reefs are monuments to Chinese ambition and symbols of the challenge facing the existing order. How the competition over these waters unfolds will shape the future of Asia—and by extension, the world.

Understanding the South China Sea is essential for anyone seeking to comprehend contemporary geopolitics. The strategic dynamics at play here—great power competition, territorial disputes, resource rivalry, alliance management—are the dynamics that will define international relations for decades to come.

Sources & Further Reading¶

• “Asia’s Cauldron: The South China Sea and the End of a Stable Pacific” by Robert D. Kaplan — The essential introduction to South China Sea geopolitics, combining geographic analysis with strategic assessment of competing claims.
• “The South China Sea: The Struggle for Power in Asia” by Bill Hayton — Detailed account of the historical claims, island-building campaigns, and diplomatic confrontations that define the dispute.
• “The South China Sea Arbitration Award” (Permanent Court of Arbitration, 2016) — The primary legal document rejecting China’s expansive claims, essential reading for understanding the international law at stake.
• “Island Wars: The Clash of Imperial Powers in the Pacific” by John W. Dower — Historical context for understanding how island territories in Asia have been contested across centuries.
• “The Hundred-Year Marathon: China’s Secret Strategy to Replace America as the Global Superpower” by Michael Pillsbury — Provides one interpretation of Chinese strategic thinking that helps explain Beijing’s assertiveness in the South China Sea.