“The presence of these sensor-equipped ships suggests that China is likely engaged in some level of intelligence-gathering,” a South Korean defense official said to Korea JoongAng Daily, a first in which Seoul has verified that Chinese warships in waters close to its coastline carry sophisticated reconnaissance technologies. In a mere five months, Chinese naval vessels penetrated South Korean-controlled waters in the Yellow Sea around 170 times, a South Korean military report published by Korea JoongAng Daily and Newsweek says.
What makes this current presence stand out is not merely the number of deployments by the Chinese, but the level of technical capabilities of the ships they deployed and how close they got to key American military installations. Chinese vessels have regularly operated inside 37 miles of South Korean territorial waters off the west coast of Eocheong Island, just 88 miles from Kunsan Air Base, home to the U.S. Air Force’s Eighth Fighter Wing. These are not standard patrol boats; they are also fitted with sea surveillance radar and electronic intelligence packages that can track flight operations, signal communications, and electronic transmissions from “hundreds of miles” away.
The technical core of such intelligence collection is the People’s Liberation Army Navy’s Type 815G class electronic reconnaissance ship. These ships, the Tianwangxing and Haiwangxing among them, are optimized for high-endurance operations and carry a range of sensors and antennas that permit the interception of radar, radio, and other electronic emissions at long range. As explained in Maritime Executive, the ships can stay on station for long periods, gathering information on the electronic “signatures” of foreign military assets, tracing out communications networks, and even possibly picking up vulnerabilities in an adversary’s operations.
The strategic ramifications of such deployments are immense. The Yellow Sea’s Provisional Measures Zone (PMZ) where these incidents are most dense is a 230-mile-wide zone of overlapping Exclusive Economic Zones (EEZs) between South Korea and China. The absence of a fixed maritime boundary has provided a gray area where such intelligence activities abound. South Korea has been alerted by China’s declaration of “no-sail zones” for military training purposes within the PMZ, some of which coincide with South Korea’s EEZ, and the deployment of structures that Seoul suspects might be part of a larger push to change the status quo in Beijing’s favor, as Newsweek reports.
Along with shipborne monitoring, China has also placed at least 13 surveillance buoys in the Yellow Sea, three as recently as May 2023. Each about 20 feet tall, they are technically billed by Beijing as aquaculture facilities, but South Korean officials caution that they could be a potential military surveillance purpose. The positions of the buoys some inside the PMZ, others off the coast of the South Korean EEZ enable constant, unmanned surveillance of maritime and electronic activity to complement the intelligence accumulated by ships.
Chinese surveillance sophistication is matched by strategic analysis that goes beyond observation. As Senior Research Fellow Shin Beom-chul of the Sejong Institute explained to Korea JoongAng Daily, “It’s possible that China is using this as an opportunity to test its expanded naval power, strengthened through its Belt and Road Initiative, and may be targeting U.S. military bases near the Yellow Sea.” This fits into a larger trend in the Indo-Pacific, where China’s navy has been increasingly deploying intelligence-gathering vessels far from home oceans to watch multinational exercises and foreign military activities, such as during the Talisman Sabre exercise off Australia.
Technically, the development of naval intelligence gathering has been influenced by the progress in remote sensing, signal processing, and data analysis. Contemporary ocean surveillance vessels such as the Type 815G employ combined sensor arrays, high-gain antennas, and real-time data links to transmit enormous quantities of intercepted data to onshore command centers. The increased dependency on digital communications and high-intelligence networked battle systems by today’s militaries is both an opportunity and a weakness: far-borne, high-bandwidth communications can be compromised and examined, disclosing operational practices and technical data that were previously much more difficult to acquire.
The South Korean and American response is still in the works. While both countries are busy fending off the North Korean military threat, the growing Chinese naval presence in the Yellow Sea is compelling a rethink on maritime security and intelligence procedures. South Korea’s navy has already started deploying assets to keep a watch on Chinese movements in the PMZ, and Seoul and Washington are evaluating how to protect sensitive military activities from snooping electronic eyes.
The technical and strategic chess match unfolding in the Yellow Sea underscores the centrality of electronic intelligence in modern naval competition. As remote sensors, unmanned systems, and advanced surveillance ships proliferate, the ability to operate undetected and to detect others will remain a defining feature of maritime security in the Asia-Pacific.
