One Sea, Many Claims
The South China Sea is one of the world's most strategically vital bodies of water. It spans roughly 3.5 million square kilometres, connecting the Pacific and Indian Oceans. Every year, an enormous share of global maritime trade passes through its waters — including vast quantities of oil, liquefied natural gas, and manufactured goods. It is also home to rich fishing grounds and potentially significant undersea energy reserves.
And almost every inch of it is disputed.
Who Are the Claimants?
| Country | Key Claims |
|---|---|
| China | Claims most of the sea via the "nine-dash line," including areas close to other nations' coasts |
| Vietnam | Claims the Paracel and Spratly Islands and surrounding waters |
| Philippines | Claims its Exclusive Economic Zone (EEZ) and portions of the Spratlys |
| Malaysia | Claims parts of the Spratly Islands and its EEZ |
| Brunei | Claims a small EEZ area overlapping with China's nine-dash line |
| Taiwan | Makes claims nearly identical to China's, rooted in the same historical maps |
China's Nine-Dash Line
The most sweeping and controversial claim comes from China, which asserts historical sovereignty over the majority of the South China Sea using a boundary known as the "nine-dash line." This line extends hundreds of kilometres from China's coast, overlapping significantly with the internationally recognised EEZs of Vietnam, the Philippines, Malaysia, and Brunei.
In 2016, an international tribunal at The Hague — convened under the UN Convention on the Law of the Sea (UNCLOS) — ruled that China's nine-dash line claim had no legal basis under international law. China rejected the ruling outright and has continued to expand its presence in the region.
What China Has Been Building
Over the past decade, China has engaged in large-scale island-building projects in the Spratly Islands, converting reefs and shoals into artificial islands equipped with airstrips, radar systems, missile batteries, and military installations. This transformation of geography into military infrastructure has dramatically shifted the balance of power in the region and raised alarm among neighbouring states and Western governments.
The United States' Role
The U.S. is not a claimant, but it has significant strategic interests in maintaining freedom of navigation. The U.S. Navy regularly conducts Freedom of Navigation Operations (FONOPs) — sailing warships through waters China claims as its own — to challenge what Washington views as unlawful maritime claims. These operations have led to tense standoffs at sea and sharp diplomatic exchanges.
The U.S. also has a mutual defence treaty with the Philippines, meaning an armed attack on Philippine vessels could trigger American military involvement.
Why This Matters Globally
- Trade flows: A significant portion of global seaborne trade transits the South China Sea annually, making stability here a global economic concern.
- Energy security: The seabed may contain substantial oil and gas reserves, though estimates vary widely.
- Military escalation risk: Multiple navies operate in close proximity. A miscalculation or accident could rapidly escalate.
- Precedent for international law: If large nations can simply ignore international tribunal rulings, the rules-based global order is fundamentally weakened.
The Path Forward
Diplomatic efforts, including ASEAN-led discussions and bilateral negotiations, have produced codes of conduct but no binding resolution. The dispute is deeply tied to Chinese domestic politics, national identity, and great-power ambitions — making a near-term resolution unlikely. Understanding the competing claims and their implications is essential for anyone following 21st-century geopolitics.