This February, Beijing vowed to increase China Coast Guard (CCG) patrols around the Taiwan-administered Kinmen islands following an incident between Taiwan’s Coast Guard Administration (CGA) and a Chinese motorboat. The CGA has since reported numerous cases in which CCG vessels entered the restricted and prohibited waters around Kinmen and Matsu. But both Taiwan and the mainland have been inconsistent in reporting such incidents, making it difficult to know how Beijing’s activities around the islands compare to previous years.
To answer that, AMTI analyzed automatic identification system (AIS) data from 2020 to 2024 showing CCG patrols within the prohibited and restricted waters around Kinmen and Matsu. The data indicates that while CCG activity in previous years may have been greater than reported, its vessels clearly entered the prohibited and restricted waters more often in 2024.
A History of Tensions at Kinmen and Matsu
The Kinmen and Matsu islands have been frequent sites of friction between Taipei and Beijing due to their proximity to the mainland. In the 1950’s the islands were at the center of the First and Second Taiwan Strait Crises, when they were heavily shelled by artillery fire that continued intermittently until 1979. In more recent years, Beijing has employed grey zone tactics around Kinmen and Matsu, including sending dredging fleets of up to 200 boats to the waters around the Matsu islands, taxing the patrol capabilities of Taiwan’s CGA.
A particularly fraught encounter occurred on February 14, when a Chinese motorboat entered the prohibited waters of Kinmen. The motorboat refused to submit to a search by a Taiwanese coast guard vessel, attempted to flee, but then capsized after a collision between the two boats. The incident ended with the deaths of two Chinese nationals, leading Beijing to declare on February 18 that it would be increasing patrols in the waters near Kinmen and other areas of Taiwan.
The February 14 incident and Beijing’s response drew attention to Taiwan’s prohibited and restricted waters, boundaries which have their origins in Taiwan’s 1992 Cross-Strait Act (“Act Governing Relations between the People of the Taiwan Area and the Mainland Area”). Article 29 of the act defines areas of prohibited and restricted waters around Taiwan where mainland vessels and aircraft may not enter without permission and authorizes “any necessary defensive action” to expel or apprehend violators. The corresponding boundaries published in 1993 by Taiwan’s Ministry of National Defense set the extent of the prohibited and restricted waters around the majority of Taiwan at 12 and 24 nautical miles from the low water line, respectively—equivalent to the extent of the territorial sea and contiguous zone defined by the UN Convention on the Law of the Sea. But around Kinmen and Matsu islands (as well as Itu Aba in the South China Sea), it set smaller boundaries of just 2.2 and 3.2 nautical miles (4 and 6 kilometers). While the mainland has never officially recognized the prohibited or restricted waters, Taiwan’s Mainland Affairs Council maintains that both sides have tacitly abided by the boundaries since they were set. But that understanding appears to be eroding.
A Look at the Data
AMTI analyzed AIS data from May 2020 through September 2024 from CCG vessels active in the restricted and prohibited waters around the islands. Each transmission from a unique vessel on a unique date from within prohibited or restricted waters was counted as an entrance (multiple transmissions from a ship at a single location within the same day were only counted as one entrance). The incomplete nature of AIS data, which often contains gaps in transmissions, means that these numbers are only a baseline, and the true number of entrances is almost certainly higher.
A total of 156 unique CCG vessels were found to have broadcast their position from within restricted and prohibited waters around the Kinmen and Matsu islands over the period, for a total of 2,012 entrances.
Overall, the trend in both the number of entrances as well as the number of unique entering vessels follow the same V-shaped trajectory, beginning moderately high in 2020 before falling sharply in 2022, recovering in 2023, peaking in 2024.
The highest number of entrances occurred in March 2024, which is consistent with Chinese statements pledging to increase patrols following the February 14 incident. The lowest number of entrances occurred in June 2022, suggesting that while tensions were high between Taipei and Beijing during this period, Chinese patrols were not focused on Taiwan’s outer islands – but possibly instead around air incursions into Taiwan’s Air Defense Identification Zone.
The data shows that Taiwan’s CGA has faced an average of 13 entrances per week across the islands in 2024. This is more than 3 times as much as in 2022, but only slightly more than the average of 11 entrances per week in 2020.
The CCG was more active in Kinmen county than the Matsu islands throughout the period. Among the seven islands and island groups that make up Kinmen and Matsu, (Kinmen, Wu Qiu, Dongding; Matsu, Dongyin, Juguang, Liang Island), Kinmen island itself was also consistently the most frequented location, matching the frequency of media reports on the area.
Conclusion
Given the sharp rise in cross-strait tensions since 2020, the current peak of CCG entrances around Kinmen and Matsu is likely an all-time high. And while AIS data can provide important insights into quantitative trends, reports indicate that the character of CCG activities is also changing. In May, a record 11 Chinese government vessels entered waters around Kinmen island simultaneously, some of them conducting a maritime exercise with Chinese fishing boats. And in October, CCG ships entered restricted waters around Matsu as part of Chinese military exercises simulating a blockade of Taiwan. With a high frequency of more complex activities around the islands, Taipei will be forced to stretch the resources of the CGA to respond if it hopes to maintain the regime of prohibited and restricted waters. But, as in the South China Sea and East China Sea, more frequent encounters between coast guards will inevitably create additional chances for unintended escalation.
Cover photo: I-Hwa Cheng/Bloomberg via Getty Images
