The Geopolitics of the South China Sea

Why the South China Sea Matters

The South China Sea is a semi-enclosed sea of the western Pacific, bordered by China and Taiwan to the north, the Philippines to the east, Malaysia, Brunei and Indonesia to the south, and Vietnam to the west. Its strategic value comes from three things at once: trade, energy and fish. Control of its features and waters would give a state leverage over the economic lifeline of East Asia.

• Trade: about one third of the world's shipping by value passes through the sea, including the bulk of the energy imports of China, Japan and South Korea, most of it funnelling through the Strait of Malacca.
• Energy: the seabed holds significant, though disputed, reserves of oil and natural gas, which every claimant wants to exploit within its own zone.
• Fisheries: the sea is one of the world's most productive fishing grounds and a vital protein source for the surrounding populations, so fishing rights are themselves a source of clashes.
• The main disputed features are two archipelagos, the Paracel Islands in the north and the Spratly Islands in the south, together with isolated features such as Scarborough Shoal and the Second Thomas Shoal.
• Most of these features are tiny reefs, rocks and low-tide elevations rather than true islands, which matters greatly in law, because only certain features generate maritime zones.
• The concept of geopolitics, the effect of geography on power and politics, is illustrated here perfectly: a few square kilometres of reef become vital because of where they sit astride the sea lanes.

The Claimants and the Nine-Dash Line

Seven governments assert claims, but they are not of equal scope. China's claim is by far the largest and is the source of most of the tension, because it overlaps with the claims of almost every other state and with waters that international law would assign to them.

• China and Taiwan make essentially the same expansive historical claim, each based on the nine-dash line, a U-shaped line enclosing most of the sea.
• The nine-dash line was set out by China in a note to the United Nations in 2009; in 2023 China published a version showing a tenth dash near Taiwan, so it is sometimes now called the ten-dash line.
• Vietnam claims both the Paracel and the Spratly Islands in full and has the longest-running rival claim to China's.
• The Philippines claims part of the Spratlys (which it calls the Kalayaan Island Group) and Scarborough Shoal, both close to its coast.
• Malaysia and Brunei claim features and waters in the south within the zones their coastlines generate, and Indonesia's Natuna waters are affected at the sea's southern edge although Indonesia does not consider itself a claimant to the islands.
• The core objection to the nine-dash line is that it claims waters far from China's coast and deep inside the zones that other states are entitled to under the law of the sea, without a clear legal definition of what the line even means.
• Terms to know: an Exclusive Economic Zone, or EEZ, extends 200 nautical miles from a coastal state's baseline and gives it rights over the resources of the sea and seabed there.

The Law and the 2016 Ruling

The legal framework is the United Nations Convention on the Law of the Sea, known as UNCLOS, which China, the Philippines and Vietnam have all ratified. In 2013 the Philippines took China to arbitration under UNCLOS, and the 2016 award is the single most important legal event in the dispute.

• UNCLOS sets the rules for territorial seas (12 nautical miles), exclusive economic zones (200 nautical miles) and the continental shelf, and defines which features count as islands, rocks or low-tide elevations.
• Under UNCLOS an island generates a full EEZ; a rock that cannot sustain human habitation generates only a 12-mile territorial sea; and a low-tide elevation generates no zone of its own.
• In 2016 an arbitral tribunal at The Hague, constituted under UNCLOS, ruled overwhelmingly in favour of the Philippines.
• The tribunal held that China's nine-dash line has no legal basis, because any historic rights were extinguished where they conflict with the EEZ regime of UNCLOS.
• It found that none of the Spratly features is a full island generating an EEZ, and that several features, including Mischief Reef and Second Thomas Shoal, lie within the Philippine EEZ.
• It found that China had violated the Philippines' rights by interfering with fishing and oil exploration, building artificial islands, and failing to prevent Chinese fishing in Philippine waters.
• Trap: China rejected the ruling, refused to take part in the case, and does not recognise the award; the tribunal has no enforcement power of its own, so the ruling shapes the legal and diplomatic argument rather than settling the dispute on the water.

Island-Building, Grey-Zone Tactics and Flashpoints

Since about 2013 China has changed the physical and military reality of the sea faster than any legal process could keep up, using construction and coercion that stops short of open war.

• China has carried out massive land reclamation, turning submerged reefs in the Spratlys into artificial islands and building runways, ports, radar and missile facilities on features such as Fiery Cross, Subi and Mischief Reefs.
• Grey-zone tactics: China relies on its coast guard and a maritime militia of fishing vessels, rather than the navy, to assert control, so that pressure stays below the threshold that would trigger a military response.
• Scarborough Shoal: after a 2012 standoff China took effective control of this rich fishing ground close to the Philippine coast, and it remains a flashpoint.
• Second Thomas Shoal: the Philippines grounded a warship, the BRP Sierra Madre, there in 1999 to mark its claim, and stations marines on the rusting hull; Chinese vessels repeatedly try to block Philippine resupply missions.
• In June 2024 the China Coast Guard blocked and damaged Philippine boats resupplying the Sierra Madre and injured several sailors, one seriously, in the most serious incident in years.
• The United States has a mutual defence treaty with the Philippines and has said it covers armed attacks in the South China Sea; it also runs freedom of navigation operations, sailing warships near the disputed features to reject excessive claims.
• The Association of Southeast Asian Nations, ASEAN, has negotiated with China for years over a binding Code of Conduct for the sea, but progress has been slow and the group is divided.

The Wider Contest and Why It Endures

The South China Sea is a local territorial dispute and, at the same time, a stage for the central geopolitical rivalry of the century, between a rising China and the United States and its allies. That double character is why it is so hard to resolve.

• For China the sea is part of the first island chain, and control of it protects its southern coast, its trade routes and its nuclear submarine base on Hainan, so it treats the claim as a core interest.
• For the United States the issue is freedom of navigation and the credibility of its alliances; conceding the sea would weaken its position across the Indo-Pacific.
• Other powers are drawn in: Japan, Australia, India and European states increasingly send ships or issue statements, and groupings such as the Quad (the United States, Japan, India and Australia) frame the region as the Indo-Pacific.
• Vietnam, Malaysia and others hedge, deepening ties with the United States while avoiding open confrontation with China, their largest trading partner.
• The dispute endures because the stakes are high, the claims overlap, the law is rejected by the strongest claimant, and no side can back down without a loss of face or strategic position.
• Strategy for study: keep the three layers separate in your mind, the resources and geography, the legal position under UNCLOS, and the great-power rivalry; most exam questions and news stories sit in one of these three layers.

Key Terms

Nine-dash line

The U-shaped line, first submitted by China to the United Nations in 2009, that encloses most of the South China Sea as the basis of its claims. A 2016 tribunal ruled it has no legal basis; a ten-dash version appeared in 2023.

Exclusive Economic Zone (EEZ)

Under UNCLOS, the zone extending 200 nautical miles from a state's coastal baseline within which it has sovereign rights over the natural resources of the sea and seabed. Much of the dispute is about whose EEZ covers which waters.

UNCLOS

The United Nations Convention on the Law of the Sea, the treaty that defines maritime zones and the status of islands, rocks and low-tide elevations. It provided the legal framework for the 2016 arbitration.

Grey-zone tactics

Coercive actions kept deliberately below the threshold of open warfare, such as China's use of its coast guard and maritime militia to assert control without triggering a military response.

Practice Quiz — 20 Questions

1. Roughly what share of global shipping by value passes through the South China Sea?

   • A.About one tenth
   • B.About one third
   • C.About one half
   • D.Almost all
   B. About one third — About a third of world shipping passes through the sea, making it a vital global trade artery.

2. The two main disputed archipelagos in the South China Sea are the Spratly Islands and the:

   • A.Paracel Islands
   • B.Ryukyu Islands
   • C.Kuril Islands
   • D.Andaman Islands
   A. Paracel Islands — The Paracels in the north and the Spratlys in the south are the two main groups in dispute.

3. China's expansive claim to the South China Sea is represented by the:

   • A.Line of Actual Control
   • B.Nine-dash line
   • C.McMahon Line
   • D.Wallace Line
   B. Nine-dash line — The nine-dash line, submitted to the UN in 2009, encloses most of the sea.

4. In which year did China first formally submit the nine-dash line to the United Nations?

   • A.1999
   • B.2009
   • C.2016
   • D.2023
   B. 2009 — China set out the nine-dash line in a note verbale to the UN in 2009.

5. Which country, besides China, makes essentially the same historical claim based on the same line?

   • A.Vietnam
   • B.The Philippines
   • C.Taiwan
   • D.Malaysia
   C. Taiwan — Taiwan makes essentially the same expansive claim as mainland China.

6. An Exclusive Economic Zone under UNCLOS extends how far from a state's baseline?

   • A.12 nautical miles
   • B.24 nautical miles
   • C.200 nautical miles
   • D.500 nautical miles
   C. 200 nautical miles — An EEZ extends 200 nautical miles, giving the coastal state rights over resources there.

7. The treaty that defines maritime zones and the status of islands and rocks is:

   • A.UNCLOS
   • B.the Geneva Convention
   • C.the Treaty of Tordesillas
   • D.the Kyoto Protocol
   A. UNCLOS — The United Nations Convention on the Law of the Sea (UNCLOS) sets these rules.

8. Which country brought the 2013 arbitration case against China over the South China Sea?

   • A.Vietnam
   • B.The Philippines
   • C.Malaysia
   • D.Indonesia
   B. The Philippines — The Philippines initiated the case; the award came in 2016.

9. What did the 2016 arbitral tribunal rule about the nine-dash line?

   • A.That it was fully valid
   • B.That it had no legal basis
   • C.That it applied only to the Paracels
   • D.That it should be redrawn
   B. That it had no legal basis — The tribunal held that the nine-dash line has no legal basis under UNCLOS.

10. How did China respond to the 2016 ruling?

    • A.It accepted and implemented it
    • B.It rejected the ruling and refused to take part
    • C.It appealed to the UN Security Council
    • D.It withdrew all its claims
    B. It rejected the ruling and refused to take part — China boycotted the case and does not recognise the award, which has no enforcement mechanism.

11. Under UNCLOS, a rock that cannot sustain human habitation generates only a:

    • A.Full 200-mile EEZ
    • B.12-mile territorial sea
    • C.No maritime zone at all
    • D.100-mile fishing zone
    B. 12-mile territorial sea — Such a rock generates only a 12-mile territorial sea; a low-tide elevation generates none.

12. China's turning of submerged reefs into military outposts is known as:

    • A.Land reclamation or island-building
    • B.Dredging rights
    • C.Continental drift
    • D.Reef farming
    A. Land reclamation or island-building — Since about 2013 China has built artificial islands with runways and radar on Spratly reefs.

13. Which term describes China's use of its coast guard and fishing militia to assert control short of war?

    • A.Blitzkrieg
    • B.Grey-zone tactics
    • C.Blockade
    • D.Containment
    B. Grey-zone tactics — Grey-zone tactics stay below the threshold that would trigger a military response.

14. The Philippines marks its claim to Second Thomas Shoal with a grounded warship called the:

    • A.USS Nimitz
    • B.BRP Sierra Madre
    • C.HMS Prince of Wales
    • D.INS Vikrant
    B. BRP Sierra Madre — The Philippines grounded the BRP Sierra Madre there in 1999 and stations marines on it.

15. Which shoal did China take effective control of after a 2012 standoff with the Philippines?

    • A.Scarborough Shoal
    • B.Mischief Reef
    • C.Fiery Cross Reef
    • D.James Shoal
    A. Scarborough Shoal — China has controlled the rich fishing ground of Scarborough Shoal since the 2012 standoff.

16. The serious June 2024 incident at Second Thomas Shoal involved China blocking a Philippine:

    • A.Oil rig
    • B.Resupply mission to the Sierra Madre
    • C.Fishing tournament
    • D.Naval exercise with Japan
    B. Resupply mission to the Sierra Madre — China Coast Guard vessels blocked and damaged resupply boats and injured several sailors.

17. The United States asserts its position in the sea partly through:

    • A.Freedom of navigation operations
    • B.Annexing reefs
    • C.Joining the nine-dash line
    • D.Withdrawing from the region
    A. Freedom of navigation operations — US warships sail near disputed features in freedom of navigation operations to reject excessive claims.

18. Which regional organisation has long negotiated a Code of Conduct with China for the sea?

    • A.ASEAN
    • B.NATO
    • C.the European Union
    • D.the African Union
    A. ASEAN — ASEAN, the Association of Southeast Asian Nations, has sought a binding Code of Conduct.

19. The grouping of the United States, Japan, India and Australia associated with the Indo-Pacific is the:

    • A.Quad
    • B.G7
    • C.BRICS
    • D.OPEC
    A. Quad — The Quad is the quadrilateral security dialogue of the four countries.

20. For China, controlling the South China Sea is part of securing the:

    • A.first island chain
    • B.Northwest Passage
    • C.Silk Road only
    • D.Panama route
    A. first island chain — The sea lies within the first island chain, protecting China's coast, trade routes and submarine base on Hainan.

References

• Permanent Court of Arbitration, The South China Sea Arbitration (Philippines v China), 2016 — https://pca-cpa.org/en/cases/7/
• United Nations Convention on the Law of the Sea (UNCLOS) — https://www.un.org/depts/los/convention_agreements/texts/unclos/unclos_e.pdf
• US Congressional Research Service, China-Philippines Tensions in the South China Sea — https://www.congress.gov/crs-product/IF12550
• Center for Strategic and International Studies, Asia Maritime Transparency Initiative — https://amti.csis.org/
• Encyclopaedia Britannica, South China Sea — https://www.britannica.com/place/South-China-Sea