China’s quiet push in the Yellow Sea poses serious threat to Korean sovereignty

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China’s quiet push in the Yellow Sea poses serious threat to Korean sovereignty

Published: 11 Jul. 2025, 00:03

Audio report: written by reporters, read by AI

Kim Jung-ha

The author is an editorial writer at the JoongAng Ilbo.

The first territorial threat to Korea since its founding came 75 years ago from the North. Today, a second encroachment is unfolding — this time from the West. Unlike the direct and violent nature of the Korean War, China’s so-called “Yellow Sea project” is progressing slowly and quietly, making it harder for the public to sense its gravity. Yet the consequences could be severe if China succeeds in turning the Yellow Sea into its own inland sea.

An “inland sea” is a body of water enclosed by land and connected to the open sea only by a narrow passage. In contrast to territorial waters, where foreign vessels retain the right of innocent passage, inland seas allow the coastal state full control, much like land territory. If China effectively declares the Yellow Sea as such, it would mark a substantial expansion of its sovereignty toward the Korean Peninsula, with clear implications for Korea’s national security.

A closer look at China’s claimed “marine observation buoys” installed in and around the Provisional Measures Zone in the West Sea. Clockwise from top left: “Carbon Dioxide Flow Monitoring Buoy”, “China Marine Surveillance Buoy QF219” , “China Marine Monitoring Buoy QF209” and “China Marine Surveillance Buoy QF111.″ [REPUBLIC OF KOREA NAVY]

China’s claims are inconsistent with international law. In 2000, Korea and China signed a fisheries agreement that designated overlapping exclusive economic zones (EEZ) in the Yellow Sea as a Provisional Measures Zone (PMZ), managed jointly by both countries. Within the PMZ, fishing is allowed, but the construction of facilities and resource development is prohibited.

However, since 2018, China has unilaterally installed several large steel-frame structures in the zone, claiming they are for aquaculture. Although nominally fishing-related, these platforms can easily be repurposed for military use. Korea’s Ministry of Foreign Affairs has lodged formal protests, but China has not responded. In February, when Korea’s research vessel Onnuri approached the area to conduct an investigation, China deployed two large vessels and three inflatable boats to physically block the operation. Reports indicate that one of the Chinese personnel even threatened Korean researchers with a weapon.

These installations appear designed to serve as a pretext for China to declare sovereignty over the Yellow Sea in the future — mirroring its strategy in the South China Sea. There, China has built artificial islands and asserted expansive claims, including a so-called “nine-dash line” that reaches over 1,000 kilometers (621 miles) from its mainland, encroaching on the waters near Indonesia. In 2016, the Permanent Court of Arbitration ruled the claim invalid. China has ignored the ruling ever since. International law has proven ineffective in the face of power politics.

China’s Yellow Sea strategy is part of a long-term plan to protect the politically and economically strategic corridor stretching from the Bohai Gulf to Beijing. This is not a temporary campaign that can be expected to fade with time or a change in leadership. Even if the Xi Jinping administration ends, future Chinese governments are likely to continue pursuing the same objective.

Japan’s claim over Dokdo, by contrast, is not an immediate threat. As long as the Korea-U.S.-Japan security partnership remains intact, Korea’s sovereignty over Dokdo is secure. But China’s actions in the West Sea are already altering the status quo. The threat is not hypothetical — it is real and growing. In many respects, it is far more serious than the Dokdo dispute.

Korea must respond with a long-term, consistent strategy that transcends administrations. If China refuses to dismantle its structures, Korea should consider installing similar facilities in response. Vietnam’s construction of artificial islands in the South China Sea provides a useful precedent. Korea should also work closely with the United States, Japan and other members of the international community to mount a coordinated response. Strengthening naval power is equally essential. The 13.2 trillion won ($9.6 biillion) the government plans to distribute as consumer vouchers in its latest supplementary budget could instead fund the construction of 10 King Jeongjo-class Aegis destroyers.

An aerial view of Southwest Cay, also known as Pugad Island, controlled by Vietnam and part of the Spratly Islands in the disputed South China Sea, April 21, 2017. [REUTERS/YONHAP]

Above all, Korea needs strong national resolve to defend its maritime sovereignty.

Yet concern remains. When the National Assembly passed a resolution on July 3 condemning China’s installation of structures in the Yellow Sea, seven lawmakers from the broader ruling coalition abstained. They included Democratic Party lawmakers Kim Young-bae, Lee Ki-heon and Hong Ki-won; New Reform Party member Shin Jang-sik; and Progressive Party lawmakers Son Sol, Jeon Jong-deok and Yoon Jong-oh. For sitting members of the legislature to hesitate on such a critical issue raises questions about their commitment to national sovereignty.

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.