territorial disputes in the South China Sea, series of conflicts arising from the overlapping territorial claims of several countries that border the South China Sea. In recent decades China has been widely seen as the conflicts’ primary driver. While countries have long disagreed on the sea’s precise international demarcations, China has moved ever closer to demanding exclusive economic and military rights over the vast majority of the South China Sea. While their claims and approaches differ, Chinese and Taiwanese officials both have argued that the South China Sea constitutes “historical waters.” They have represented their claims, encompassing roughly 90 percent of the sea, on maps by using a U-shaped boundary line made up of nine to 11 dashes (commonly known as the “nine-dash line”). This line’s geographic coordinates and legal basis are vague and conflict with the United Nations Convention on the Law of the Sea (UNCLOS). The primary countries affected by the Chinese territorial claims are Vietnam, the Philippines, Malaysia, and Brunei, but many stakeholders from outside the region, most notably the United States, have become involved in the disputes and have aimed to check Chinese ambition.

　　Paracel Islands, South China Sea

　　Spratly IslandsThe South China Sea—known in Vietnam as the East Sea and in the Philippines as the West Philippine Sea—is the area of the Pacific Ocean bounded by Southeast Asia to the west, China to the north, Taiwan and the Taiwan Strait to the northeast, the Philippines to the east, and the Indonesian archipelago to the south. The sea contains strategically vital shipping lanes, which, according to a 2017 study conducted by ChinaPower (a project of the Center for Strategic and International Studies), carried some $3.4 trillion in trade (constituting about one-fifth of global trade) in 2016. In the late 20th and early 21st century, undersea explorations have uncovered reserves of natural gas and crude oil in the sea, though the size of these reserves is widely contested. Key land features in the sea include the Paracel Islands, the Scarborough Shoal, and the Spratly Islands. The primary claimants in the disputes are China, Taiwan, the Philippines, Vietnam, and Malaysia. Indonesia has insisted on its neutrality in the disputes but has separately struggled with Chinese incursions into its exclusive economic zone (EEZ), a UNCLOS designation that grants coastal states exclusive rights to fishing and resource extraction in an area of up to 200 nautical miles (370 km) from their coasts.

　　The origins of the contemporary conflict over the South China Sea can be traced to changes in East Asian geopolitics following World War II (1939–45). China’s historical claims to the sea date to the so-called “11-dash line,” introduced in 1947 by the Nationalists (Kuomintang) under Chiang Kai-shek, during the Chinese Civil War (1945–49). The map that included the 11-dash line emphasized Chinese sovereignty and reflected nationalist pride after what many Chinese considered to have been a century of humiliation by foreign powers. When the Communists under Mao Zedong defeated the Nationalists in the civil war and established the People’s Republic of China, the new government in Beijing claimed successor status to the Republic of China and its nautical territorial claims, which it modified slightly by changing the 11-dash line of the 1947 map to a nine-dash line.

　　The disputes over ownership of the South China Sea remained relatively dormant until the 1970s when China began asserting its vast territorial claims after discovering potential oil and gas reserves in the sea. In 1974 China seized the Paracel Islands from South Vietnam; more than 65 Vietnamese soldiers were killed in the process. China then took possession of Johnson Reef (part of the Spratly Islands) from Vietnam in 1988 and Mischief Reef (also part of the Spratlys), claimed by the Philippines, in 1994. China now controls the Paracel Islands in their entirety. The plurality of the Spratlys’ reefs and islands are controlled by Vietnam, while the Philippines and China each claim and operate on a sizable portion of the archipelago. Malaysia and Brunei both have claimed some features of the Spratly Islands as well as EEZs off their coasts that overlap with China’s claims.

　　Since the early 21st century, an aggressive campaign of land reclamation (frequently referred to as “island building”) by China has significantly increased the country’s presence in the South China Sea. China has built military infrastructure, including naval bases and airstrips, on the reclaimed land. The Chinese also have sought to exercise their claims through nonmilitary means—for example, by sending massive fishing fleets into the EEZs of other countries. In 2014 China moved an oil rig into Vietnamese waters, sparking massive protests in Vietnam. Moreover, in attempting to block rivals’ efforts, most claimants have made arrests of foreign fishermen and sailors in waters they consider to be their own.

　　In 2013 the Philippines attempted to solve the crisis through the International Criminal Court (ICC), taking China to the arbitral tribunal under the terms of UNCLOS. In 2016 the court ruled that the nine-dash line was invalid and that in areas of conflict between Chinese historical claims and UNCLOS boundaries, the latter superseded the former. The court further ruled that China’s island building, fishing practices, and interference with Philippine fishing in areas within the Philippines’ EEZ were unlawful. The ruling was rejected by China, which refused to participate in the ICC proceedings. However, Taiwan and various other countries also rejected the court’s decision. Supporters of the ruling included the United States, Japan, and Australia. ASEAN members were largely split, and the organization failed to produce a unified statement.

　　Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now In the early 2020s tensions intensified as maritime confrontations increased, especially between China and the Philippines, leading to joint naval drills between the Philippines and the United States in the South China Sea. In August 2023 China revealed a revised map of its territory in the South China Sea, which claimed an even larger portion of the sea. A 10th dash was added to include the island of Taiwan and nearly the entirety of the Spratly Islands as Chinese territory. Several countries rejected the map.

　　AUKUS trilateral meeting(From left) Australian Prime Minister Anthony Albanese, U.S. Pres. Joe Biden, and British Prime Minister Rishi Sunak holding a press conference after a trilateral meeting during the AUKUS summit in San Diego, March 13, 2023.(more)Other territorial claimants have responded to Chinese expansion through various means. Most notably, Vietnam has also undertaken land reclamation and military buildups on island features. Indonesia and the Philippines have attempted to rally international support to prevent Chinese encroachment on their EEZs. For its part, the United States, which has no territorial claims in the region and officially maintains neutrality in the disputes, has nevertheless sought to check Chinese encroachment against its allies in the South China Sea. In a 2022 press statement U.S. Pres. Joe Biden’s administration called on China to adhere to the 2016 arbitral ruling and pledged that the United States would support its ally the Philippines in maintaining order in the region. The United States also has forged several regional security mechanisms—including AUKUS (with the United Kingdom and Australia) and the Quadrilateral Security Dialogue (comprising the United States, Australia, India, and Japan)—and has sought partnerships with some ASEAN countries. China’s ambitions in the South China Sea have deeply alienated some of its neighboring countries, driving them, some analysts argue, into the arms of the United States as the two superpowers strive to protect their national interests in the Pacific.