For many in the region, China’s claims over the South China Sea are particularly problematic.

In 2009, China startled the world by unveiling its nine-dash line—a maritime claim that sketches out Beijing’s ostensible sovereignty over the South China Sea. Though some scholars argue this strategic calculus predates its formal announcement, the concept wasn’t officially presented to the United Nations until 2009, under the auspices of a “cohesive lawful foundation.” According to an array of Chinese scholars, this claim finds its roots in antiquity, tracing back to the Han dynasty’s original identification of the South China Sea islands over two thousand years ago.

From the 10th to the 14th centuries, early Chinese cartographers insinuated that the South China Sea was part of China’s dominion. Despite this historical claim, Beijing has remained intentionally nebulous in articulating the specifics of the nine-dash line—a vagueness that has invited an array of interpretations and potential confrontations, especially given China’s proactive measures in enforcing its territorial assertions. The aim of this analysis is to elucidate the underpinnings of this enigmatic concept and its ensuing impact on China’s maritime ambitions.

Robert D. Kaplan’s seminal work, Asia’s Cauldron, traces the line’s origins to maps generated by the nationalist Kuomintang government before and during World War II. When the communists eventually seized power from the Kuomintang, the latter retreated to Taiwan, yet the idea of this maritime boundary persisted.

The nine-dash line itself is scarcely detailed. Its dashes, placed apparently at random, lack pinpoint geographic accuracy. Within this line, China asserts dominion over territorial waters that extend beyond its internationally recognized exclusive economic zone, including significant portions of the Spratly Islands, Paracel Islands, and Scarborough Shoal. Between 2014 and 2016, China escalated its territorial claims by constructing artificial landforms in these disputed regions.

Under the regulations set by the United Nations Convention on the Law of the Sea (UNCLOS), such artificial structures don’t augment China’s territorial claims. As Marina Tsirbas of the Australian National University has put it, the nine-dash line is seen as an “absolutist assertion to sovereignty and authority over every one of the elements, being land, waters, and seafloor within the area bounded by the nine-dash line.”

In recent years, international arbitration courts, based in The Hague, declared that China’s maritime claims lacked both legal substantiation and legitimacy. One would have expected this verdict to temper China’s actions; however, Beijing has capitalized on global conditions that have proven to be surprisingly favorable.

The most significant geopolitical ripple effect has been U.S. involvement. Although Washington has no explicit claims in the South China Sea, it has voiced strong objections to China’s territorial ambitions, cautioning against impeding other nations’ fishing and exploration activities. Despite not being a direct party to the disputes, the U.S. has increasingly flexed its military muscle, thereby escalating tensions and stoking regional conflict.

Within Asia, the nine-dash line contravenes UNCLOS, which limits territorial waters to twelve nautical miles. Southeast Asian nations find themselves ill-equipped to challenge Beijing unilaterally. Here, the onus may well fall on the Biden administration to counter China’s expansionist ventures and uphold international law. Without American intervention, the situation could quickly deteriorate, destabilizing the regional equilibrium.

Governments worldwide have grown increasingly uneasy with China’s bold territorial expansions in the South China Sea over the last two decades. Critical trade routes pass through these waters, including roughly 80% of the crude oil bound for Japan, Taiwan, and South Korea. Additionally, an estimated $5 trillion in global trade transits through this maritime corridor.

Countries like the Philippines, Vietnam, Malaysia, and Indonesia vehemently disagree with China’s assertions, but the dispute extends beyond these contested waters. In Aksai Chin, China and India are locked in an unyielding territorial disagreement. As China’s geopolitical clout continues to grow, there’s a palpable international concern over its rising influence. Collaborations like the Quadrilateral Security Dialogue are emerging as potential countermeasures to check Beijing’s ambitions in the Indo-Pacific region.

In this evolving landscape, the nine-dash line serves not merely as a maritime boundary but as a flashpoint—illuminating China’s increasing willingness to redefine international norms and rattle the geopolitical status quo.