Nine-dash line

The Nine-dash line is a set of nine discontinuous segments drawn on Chinese maps that encircle the majority of the South China Sea. It first appeared on a map published by the Republic of China in 1947 in the Map of the South China Sea Islands, later adopted by the People's Republic of China. The line encloses the Paracel Islands, Spratly Islands, Scarborough Shoal, and Pratas Island, extending south to the Natuna Islands and east to the Philippine archipelago. China asserts that the line represents its historical claim to the islands and waters, but it has never been accompanied by a precise list of coordinates or a formal legal definition. The claim overlaps with the exclusive economic zones (EEZs) of Vietnam, the Philippines, Malaysia, Brunei, and Indonesia, making it a focal point of regional tension.

The legal validity of the Nine-dash line has been challenged under the United Nations Convention on the Law of the Sea (UNCLOS), to which China is a signatory. In 2013, the Philippines initiated arbitration against China, leading to a ruling by the Permanent Court of Arbitration in 2016. The tribunal found that China's claim to historic rights within the line was invalid because it exceeded the limits permitted by UNCLOS, and it also ruled that several Chinese-claimed features are rocks that cannot generate an EEZ. China dismissed the ruling, asserting that the tribunal lacked jurisdiction and that its position is based on historical evidence. Many international legal scholars argue that the line is not a maritime boundary but rather a claim to the islands and waters within it, while others contend it is a claim to a “historical waters” regime not recognized by UNCLOS.

The interpretation of the Nine-dash line varies among claimants, with Taiwan historically using an eleven-dash version that excluded the Gulf of Tonkin. The line's vague nature has led to different readings: some see it as a declaration of sovereignty over the islands and a source of maritime claims, while others view it as a historical water boundary. China has often described the line as a “dotted line” indicating islands under its sovereignty, without clarifying its effect on water rights. In practice, Chinese fishing fleets and coast guard vessels operate within the line, asserting a presence that resembles a claim to the waters themselves. The ambiguity also creates difficulties for oil and gas exploration, as overlapping claims have led to standoffs between Chinese vessels and those of neighboring states.

Beyond the geopolitical headlines, the Nine-dash line has notable historical and cartographic details. The 1947 map was based on surveys conducted during the Republic of China era, and the line was initially drawn as eleven dashes, with two later removed to accommodate Vietnam's coast. The line predates the discovery of major hydrocarbon reserves in the region, suggesting that its original purpose was territorial rather than resource-driven. In the 1990s, China's 1992 Law on the Territorial Sea and Contiguous Zone referenced the line without defining it, and in 2009 it formally submitted a map to the United Nations showing the line. The line also has symbolic significance in China, where it is widely depicted in textbooks and media as a marker of national pride, even appearing on official Chinese passports. However, the lack of legal precision has led to the line being called a “claim on paper” that relies on naval power to enforce.

UNCLOS

United Nations Convention on the Law of the Sea, an international treaty defining maritime rights and boundaries.

EEZ

Exclusive Economic Zone, a sea zone extending 200 nautical miles from a coastal state's baseline, granting rights to resources.

PCA

Permanent Court of Arbitration, an intergovernmental organization that arbitrates disputes between states.