Note: Analysis of air incursions into Taiwan’s air defense identification zone (ADIZ) is current as of March 30, 2021.
In recent months, Chinese government state media outlets have frequently issued warnings to so-called “secessionist forces” allegedly stirring up trouble in Taipei, or to officials in Washington not to overstep Chinese government “red lines” when it comes to Taiwan. On March 8, at the 13th National People’s Congress, Chinese Foreign Minister Wang Yi (王毅) promised, “The two sides of the Taiwan Strait must be and will surely be reunified […] We have the capability to thwart separatist attempts for ‘Taiwan independence’ in whatever form.” Indeed, recent history has shown that whenever Washington acts to increase cooperation or support for Taiwan, Beijing shifts the cost onto Taipei—whether through economic pressure and boycotts or military threats and incursions. The pattern has become predictable, and for Taiwan, costly in a financial sense, especially in regard to the significant uptick in military incursions into Taiwan’s air defense identification zone (ADIZ).
In September 2020, Taiwan’s Ministry of National Defense (MND, 中華民國國防部) began issuing public notices on incursions into the airspace around Taiwan by the People’s Liberation Army (PLA). The decision was likely made in response to a rapid increase in PLA military incursions into Taiwan’s ADIZ. By October 2020, Taiwan’s then-Minister of National Defense Yen Teh-fa (嚴德發) stated that the PLA had conducted over 1,700 sorties into the ADIZ. The Taiwanese military response cost USD $1.09 billion (nearly 9 percent of the defense budget). In light of this, it is no wonder that the MND began to publicize these incursions: They serve as an effective demonstration of the consistent military threat that Taiwan must address daily.
The MND reports list the types and number of aircraft used in the operations, the area(s) of incursion, and the MND’s response. They also provide a map showing the flight paths, as well as photos of the PLA aircraft (see examples in the accompanying images). Between September 16, 2020 and March 30, 2021, the MND reported 135 incursions. The incursions occurred primarily in Taiwan’s southwestern ADIZ, near Pratas/Dongsha Island (東沙島), a contested island in the South China Sea that is occupied by the Taiwanese military. Only two incursions took place in the Taiwan Strait proper, on September 18 and 19, since the MND began releasing reports.
What’s in a Sortie?
After reviewing all 135 reported incursions, which included 329 total aircraft, patterns begin to emerge. The PLA deployed 14 types of aircraft: Y-8 reconnaissance (RECCE), Y-8 anti-submarine (ASW), Y-8 electronic warfare (EW), Y-9 EW, KJ-500 airborne early warning & control (AEW&C), Y-8 electronic intelligence (ELINT), H-6K, J-16, SU-30, J-10, J-11, Y-9, Y-8, and JH-7.
First, the operations seem to be primarily intended for surveillance purposes. Of the 71 reported incursions in 2020, the Y-8 ASW was used in 76 percent of them, followed by the Y-8 RECCE (roughly 24 percent) and Y-8 EW (roughly 22 percent). In the 64 reported incursions in 2021, the Y-8 ASW was used in 64 percent, followed by the Y-8 RECCE (roughly 36 percent), J-10 (18 percent), and Y-8 EW (14 percent). The increased use of the J-10 is something to look out for as incursions continue in 2021 since it is an offensive fighter jet, not a surveillance aircraft.
The PLA is aware that the Taiwanese military will respond to each incursion. Forcing jets to intercept an aircraft nearly every day will increase the operational costs and wear-and-tear on Taiwan’s military aircraft. For the PLA, the opportunity cost of sending one or two Y-8s into Taiwan’s southwestern ADIZ is minimal in comparison to the costs imposed on Taiwan for responding. Taiwan’s military has a far smaller budget and fewer resources available in comparison with China.
Second, the use of offensive aircraft has a fairly predictable pattern. In 2020, offensive aircraft were only part of three incursions: on September 18 and 19, and November 2. Out of all of the incursions reported, the two in September were perhaps the most dangerous, as J-16, J-11, and J-10 fighters all flew beyond the midpoint of the Taiwan Strait to Taiwan’s northwest. These sorties were a part of a drill conducted in response to an official visit by then-US Under Secretary of State for Economic Growth, Energy, and the Environment Keith Krach. Krach visited Taiwan to represent the US government at a memorial service for the recently deceased Lee Teng-hui (李登輝), the first democratically elected president of Taiwan. Similar drills took place in response to a visit by then-US Secretary of Health and Human Services Alex Azar in August 2020, but that drill occurred before the MND began publicly reporting PLA incursions. These incursions set a standard response for high-level American visits to Taiwan, which continued after the US Ambassador to Palau visited Taiwan in March 2021.
The crossing of the “median line” in the Taiwan Strait represented a dangerous new development. Before 2020, Chinese aircraft crossed the median line once in 2019, but never in the 20 years before. Historically, this was because the aviation balance favored Taiwan, which could use its might to enforce the tacit understanding that each side would stay on its side of the line.  However, in September 2020, the Chinese Foreign Ministry announced its assertion that there is no median line in the Taiwan Strait.
PLA incursions have escalated in 2021 in terms of frequency in the use of offensive aircraft. To date, 16 incursions have included offensive aircraft. Seven of them occurred in the first two weeks of the Biden Administration. Two additional large-scale incursions with offensive aircraft occurred after President Tsai Ing-wen (蔡英文) announced changes to her cabinet.
On March 26, the PLA conducted its largest drill of the year by sending 20 aircraft into Taiwan’s southwestern ADIZ. Four H-6Ks, ten J-16s, and two J-10s took part in the incursion, with one H-6K and one Y-8 ASW flying into the Bashi Channel to Taiwan’s southeast before turning back. Another large incursion occurred on March 29, with 10 aircraft breaching the ADIZ, some of which flew even deeper into the Bashi Channel. The Global Times published a piece bragging that the PLA also conducted a drill through the Miyako Strait to Taiwan’s east, thus surrounding Taiwan with military aircraft from both sides.
The largest incursions occurred in response to important developments in the United States and Taiwan. Responding to high-profile visits, cabinet changes, or defense plans by launching large-scale incursions, the PLA has shown that it has the military capacity to hurt Taiwan. While the PLA may not have the capability to launch a successful invasion of Taiwan yet, it does have the resources to strike any city on the island with its aircraft. The pattern of launching an operation after an important visit or event allows the PLA and Beijing to argue that Taipei or Washington “made” them do it and that if everyone acted appropriately, the incursions would not be necessary.
Looking Beyond the Incursions
The major incursions receive most of the attention from major media and foreign governments as these operations include fighter jets capable of inflicting significant damage. However, the larger drills are but a fraction of the total number of surveillance and reconnaissance missions. Responding to each and every sortie exacts a significant cost on Taiwan’s military.
If Beijing desired, it could easily outspend Taipei and complicate Taiwan’s defense budget by increasing the scope of these near-daily sorties. One way for Beijing to push Taiwan’s military to its limits would be to expand the map and become more aggressive in the Taiwan Strait, or send a starker message and conduct more frequent incursions to Taiwan’s east. Accounting for daily incursions in one predictable part of the map is easy to prepare for. However, if incursions and drills begin to occur simultaneously in Taiwan’s northwest, southwest, and southeast, then Taipei would likely be unable to afford the fuel costs or dedicate the manpower and aircraft necessary to respond to all of them.
The vast majority of the breaches thus far have occurred in the vicinity of Taiwan-occupied Dongsha Island, which is 200 miles from Hong Kong and 275 miles from Kaohsiung. It is more vulnerable to military escalation than Taiwan proper (and even Taiwan’s outlying islands off China’s coast) due to its isolation. In October 2020, Hong Kong air traffic controllers prevented a Taiwanese civilian aircraft full of military personnel from flying to the island and forced it to turn back due to “dangerous activities” occurring in the area. According to the flight transcript, no notice of Chinese military activity was given to Hong Kong as is customary when the PLA conducts a drill. Critically, the flight route for Taiwanese aircraft traveling to Dongsha falls under the authority of Hong Kong due to its proximity. The issue for the future is whether or not Beijing will one day decide to take Dongsha by force and use the Hong Kong air traffic controllers as a mechanism to try to stop Taiwan from sending additional troops there.
The question of if or when a Chinese military invasion of Taiwan will occur often disregards the more likely scenarios in the South China Sea. Given the number of breaches in Taiwan’s southwestern ADIZ near Dongsha, the area appears to be a much more likely target for military escalation than Taiwan proper. As the Biden Administration begins to formulate its strategy for countering China in the region, planning for responses and contingencies over Dongsha and other islands should be high on the list. Increasing cooperation with Tokyo for Taiwan’s northeast should be a topic for discussion. Such a strategy should also include responses to the continued incursions in the southwestern ADIZ, how best to assist Taiwan in responding to the sorties, and what to do in the event that the incursions expand beyond this particular spot.
The main point: By publishing reports of People’s Liberation Army air incursions in its air defense identification zone, Taiwan’s Ministry of Defense is shedding light on a growing problem for Taiwan’s military responses against Beijing. The true danger of these near-daily incursions is what could happen if the PLA expands its operations beyond Taiwan’s southwestern ADIZ and conducts drills on all sides of Taiwan.
 For more on the historic power balance in the Taiwan Strait, see, “Chapter 4 – Taiwan” in the 2020 Annual Report to Congress, U.S.-China Economic and Security Review Commission, December 2020, p. 457, https://www.uscc.gov/sites/default/files/2020-12/Chapter_4–Taiwan.pdf.