China’s Recent ADIZ Violations Have Changed the Status Quo in the Taiwan Strait

Ben Lewis is an independent defense analyst based in Washington D.C. focused on the People’s Liberation Army and Taiwan security issues. He manages an English-language database tracking PLA incursions in Taiwan’s Air Defense Identification Zone. Follow him on Twitter @OfficialBen_L 

Since late 2020, People’s Liberation Army (PLA) aircraft have flown sorties into Taiwan’s self-declared Air Defense Identification Zone (ADIZ) on a near daily basis. 2022 was a milestone in ADIZ violations with 1,737 PLA aircraft tracked, more than 2019, 2020, and 2021 combined. These ADIZ violations can be grouped into three categories: routine, assertive, and reactionary. China used the August 2022 visit to Taiwan by then House Speaker Nancy Pelosi to permanently change to the status quo in the Taiwan Strait by erasing the median line, the unofficial boundary between the China and Taiwan in the Taiwan strait, and each of these categories saw a change in their previous composition as a result.  

Each type of ADIZ violation is determined by the number of aircraft involved in relation to the average daily total of aircraft tracked in the ADIZ since September 2020, which stands at roughly five. Violations involving between one and five aircraft include all days at or below the average, and thus are designated routine. Violations comprised of six to nine aircraft include days above but not more than double the average and are designated assertive. Violations comprised of ten or more aircraft include all days at or above twice the average and are designated reactionary.  

The term ‘routine’ is not intended to normalize the PLA’s behavior around Taiwan; instead, such violations are intended to alter the status quo such that the presence of PLA aircraft is no longer novel. In other words, if a small number of aircraft are tracked in the ADIZ every day, the hope is that Taiwan will come to accept it as routine. In most cases, pre-August 2022 routine violations were composed of special mission and support aircraft like the Y-8G, Y-8Q, and Y-9JZ operating in the Southwest ADIZ. Post-August 2022 routine violations are similar to those that occurred prior to Speaker Pelosi’s visit, but often include more combat aircraft like the J-11, J-16, and Su-30, as well as median line crossings. 

Assertive violations are meant to keep a consistent level of pressure on Taiwan’s armed forces. Whereas routine violations may fall short of putting pressure on Taiwan’s military, in increasing the number and variety of aircraft tracked in a single day, assertive violations intensify the strain on the military resources Taiwan uses to monitor flights into the ADIZ. Pre-August 2022 assertive violations were made up of a mix of combat, special mission, and support aircraft operating in the Southwest ADIZ. Post-August 2022 assertive violations are made up of the same number and types of aircraft as pre-August 2022 assertive violations, but now typically include a greater proportion of combat aircraft, median line crossings, and aircraft tracked in more than one part of the ADIZ.  

Finally, reactionary violations involve ten or more aircraft and are intended to signal Beijing’s displeasure with a geopolitical development involving Taiwan. The PLA uses large numbers of mostly combat aircraft with some special mission and support aircraft to remind Taiwan and its supporters of the potential consequences of violating the ‘one China principle.’ Post-August 2022 reactionary violations are made up of the same number and types of aircraft as pre-August 2022 reactionary violations, but now typically also includes median line crossings and aircraft tracked in more than one location in the ADIZ. For instance, on December 25, 2022, in response to President Joe Biden signing into law the 2023 National Defense Authorization Act, which allocated $10 billion to improve Taiwan’s defensive capabilities. The PLA flew 47 aircraft into the ADIZ, with 42 (J-10, J-11, J-16, Su-30) combat aircraft, one (CH-4) combat drone, three (KJ-500, Y-8 ASW, Y-8 EW) special mission and support aircraft, and one (WZ-7) special mission and support drone. The aircraft were tracked in both the Southwest ADIZ and crossing the Median Line.  

In sum, while all three types of ADIZ violations evolved following Speaker Pelosi’s visit to Taiwan to include additional combat aircraft and median line crossings, China’s intentions are unchanged. Routine violations are used to normalize PLA behavior, assertive violations to put pressure on Taiwan’s military and harm its operational readiness, and reactionary violations to signal Beijing’s displeasure with geopolitical events.  

The implications of the PLA’s expanded ADIZ incursions for Taiwan are threefold. First, every type of violation is intended to put pressure on Taiwan’s armed forces by demanding a response. While Taiwan’s does not scramble aircraft to intercept every PLA incursion, and it is unknown what number and composition of PLA aircraft is necessary to induce such a response, every type of violation is tracked by Taiwan’s Air Defense and Missile Command and Taiwanese pilots are put on standby to respond. This negatively impacts the readiness of Taiwan’s forces while simultaneously providing PLA pilots an opportunity to train inside their future area of operations. Second, these violations function as a military pressure campaign against Taiwan, both degrading Taiwan’s sovereignty and signaling that an attack could come at any time. Finally, the unpredictable nature of ADIZ violations is intended to keep the status quo around Taiwan unstable and ambiguous in order to facilitate strategic surprise. If a Taiwan contingency operation does occur, the PLA has established a cover for the movement of large quantities of air assets around Taiwan. 

The implications for the United States are two-fold. First, the impact of these violations on Taiwan directly affects the United States should it choose to intervene on Taiwan’s behalf in an invasion scenario. The degradation in the readiness of Taiwan’s armed forces, paired with the continued development of PLA pilot experience, may hinder Taiwan’s defense effort, decreasing the amount of time U.S. forces will have to respond. Second, the PRC is attempting to establish a status quo for the use of its military forces not just around Taiwan, but across the Indo-Pacific. If PLA activities around Taiwan lose their novelty, the PRC may attempt to duplicate this kind of behavior in support of its territorial disputes elsewhere in the region. Given that these disputes include multiple U.S. treaty allies, this is a direct threat to U.S. interests and security in the region. 

PLA violations of Taiwan’s ADIZ have significant implications for both Taiwan and the United States, and it is crucial they are not normalized. Washington and Taipei should coordinate, be it through increased transits through the Taiwan Strait by U.S. and allied naval craft, flights along the median line by U.S. aircraft, intelligence sharing, or joint training exercises, to negate the negative impacts of these activities and ensure Beijing is not emboldened to intensify this kind of behavior.