The South China Sea is a marginal sea of the Western Pacific Ocean, a geographical concept that has become a major geopolitical flashpoint due to overlapping territorial claims and its strategic importance as a global shipping lane. It is bordered by China, Taiwan, Vietnam, the Philippines, Malaysia, Brunei, Indonesia, and others, and contains over 250 islands, reefs, and shoals, including the Spratly Islands and Paracel Islands. The disputes, which became more pronounced in the 1970s with the discovery of potential oil and gas reserves, center on control over rich fishing stocks, hydrocarbon deposits, and the sea's vital shipping lanes, through which an estimated one-third of global maritime trade passes annually.
The core of the conflict is China's expansive claim, represented by the vague "nine-dash line," which covers roughly 90 percent of the sea and overlaps with the Exclusive Economic Zones (EEZs) of several Southeast Asian nations. This claim is based on a concept of "historic rights". The mechanism for resolving such disputes is the United Nations Convention on the Law of the Sea (UNCLOS), a treaty that defines maritime zones like the 12-nautical-mile territorial sea and the 200-nautical-mile EEZ.
A key development was the 2016 ruling by the Permanent Court of Arbitration (PCA) in The Republic of the Philippines v. The People's Republic of China. The tribunal found that China's claim to historic rights to resources within the nine-dash line was incompatible with the provisions of UNCLOS and had no legal basis. The judgment also clarified that many features claimed by China do not qualify as islands and cannot generate full maritime zones. China, however, rejected the ruling, maintaining that its claims are based on historic rights outside the treaty.
The situation has recently changed with increased tensions, particularly between China and the Philippines, involving confrontations near features like the Second Thomas Shoal. The concept connects to the broader geopolitical rivalry between China and the United States, which conducts Freedom of Navigation Operations (FONOPs) in the region to challenge what it considers excessive maritime claims, citing UNCLOS principles.