It has been a year since then-U.S. House Speaker Nancy Pelosi (D-CA) visited Taiwan, despite China’s protests and threats of retaliation. Pelosi marked the anniversary of the visit by issuing a statement reiterating her “solidarity” with the people of Taiwan and calling Beijing’s approach to the self-governed island “cowardly.”
As we noted in these pages a year ago, Pelosi’s visit resulted in tensions in the Taiwan Strait not seen in three decades – a veritable Fourth Taiwan Strait Crisis – with Beijing imposing sanctions, initiating cyberattacks, launching large-sortie incursions into Taiwan’s air defense identification zone (ADIZ) and across the Median Line of the Taiwan Strait, firing ballistic missiles over the island, and conducting “encircling” drills around the island.
In this article we assess the changes that the People’s Liberation Army (PLA) has instituted regarding aerial incursions into Taiwan’s ADIZ since the Pelosi visit.
The Nullification of the Median Line
Prior to Pelosi’s visit (and since Taiwan’s Ministry of National Defense began making data on PLA aerial incursions into the island’s ADIZ publicly available, beginning in mid-September 2020) only two out of the 466 recorded PLA incursions involved the PLA flying sorties across the Median Line of the Taiwan Strait. Both line incursions came in response to a visit to Taiwan by U.S. Undersecretary of State Keith Krach.
On September 18, 2020, when Krach held a day of closed-door meetings with Taiwanese ministers and dined with President Tsai Ing-wen, the PLA dispatched 12 aircraft across the Median Line, and another six into the southwestern ADIZ. The next day, as Krach attended the memorial service for former President Lee Teng-hui alongside Tsai, the PLA followed up with an eight-aircaft sortie across the Median Line, with another seven aircraft entering the southwestern ADIZ.
After Krach’s visit, a Chinese Foreign Ministry spokesperson denied the existence of the Median Line, but the PLA continued to respect the informal line in practice. There were no further line crossings until the Pelosi visit.
August 2022 marked the watershed of a “new normal” regarding PLA incursions across the Median Line. The PLA initially responded to Pelosi’s visit by crossing the line with a 22 aircraft sortie on August 3, 2022, and continued with over 250 sorties across the line for the next 23 consecutive days – the longest such streak recorded in the data thus far.
In the year since Pelosi’s visit, there have been over 140 incursions across the Median Line (on average approximately once every 2.5 days), totaling more than 1,000 sorties and an average of seven aircraft per incursion. By contrast, intrusions into the southwestern ADIZ have an average of only three aircraft per incursion.
Over the past year we have seen that not all Median Line incursions are equal, however. The line incursions of August 3-5, 2022 were the most dangerous incidents in the Taiwan Strait yet, with strike package-like formations carrying out simulated attacks on high-value targets along the northern portion of the Median Line (see here, here, and here). These incursions carried unparalleled chances for miscalculation given that the distance and flight time from the line to Taipei is very short. PLA aircraft could appear above the capital city within minutes, putting additional pressure on Taiwanese pilots and decision-makers.
We again witnessed these high-risk intrusions across the Median Line on April 8-9 of this year, as the PLA responded to Tsai’s meeting with U.S. House Speaker Kevin McCarthy in California by holding “combat drills” around the island (see here, here, and here).
However, these large-scale (20+ sorties) and high-risk Median Line incursions are relatively rare (six of 142 line incursions or 6.3 percent). The modal sortie size for Median Line incursions is one. Over half of the incursions (76 of 142) involve five sorties or fewer, and three-fourths (74.6 percent) involve 10 sorties or fewer.
These smaller incursions are a key part of the PLA’s “new normal,” aimed at maintaining and sustaining pressure across the Median Line – with sorties appearing as disparate groups of relatively fewer aircraft along different points. This tests the reactions of the Republic of China Air Force, forcing it to scramble quick reaction alert aircraft from several air bases in response. These frequent incursions have effectively nullified the status quo ante in the Taiwan Strait.
Further, Beijing has used these smaller line incursions to signal its displeasure with continued high-level U.S. political engagement with Taiwan. Nine more congressional delegations (CODELs) followed the Pelosi visit, and it is noticeable that the pattern of line crossings associated with these follow-on CODEL visits were significantly less threatening than those linked to Pelosi’s (see for example here, here, and here). Visits to Taiwan by the governor of Indiana, Eric Holcomb, the governor of Arizona, Doug Ducey, and the governor of Virginia, Glenn Youngkin, also resulted in PLA sorties across the Median Line as they met with Tsai (see here, here, and here).
We also saw an increase in line incursions when the United States and Taiwan announced the start of formal trade talks as part of the U.S.-Taiwan Initiative on 21st-Century Trade, when the U.S. Senate Foreign Relations Committee advanced the Taiwan Policy Act, and when the House and Senate approved the Taiwan Enhanced Resilience Act.
The Rise of Multi-Zone Incursions
The PLA’s post-Pelosi nullification of the Median Line has contributed to the rise of multi-ADIZ incursions. As we noted above, prior to the Pelosi visit the PLA’s incursions were almost exclusively limited to Taiwan’s southwestern ADIZ. Since then, however, we have seen instances of incursions not just into the southwestern ADIZ (252) and across the Median Line (143), but also into the island’s southeastern (43), eastern (11), and northeastern (16) ADIZs as identified by Taiwan’s MND.
It is interesting to note that incursions into the southeastern ADIZ are dominated by Z-9 anti-submarine warfare helicopters and unmanned aerial vehicles (UAVs) as they circumnavigate the island or traverse up the eastern coast before turning around. In the case of the eastern ADIZ, incursions consist predominantly of ship-borne helicopters and UAVs dispatched east of Taiwan. This also underscores increased and more constant PLA naval activity to the east of the island.
That said, however, single-zone incursions continue to be the norm. Out of 293 post-Pelosi incursions, 155 (52.9 percent) occurred in a single zone; 111 (37.9 percent) occurred in two zones; 23 (7.8 percent) occurred in three zones; and just four (1.4 percent) occurred in four zones.
Of the 155 single-zone incursions, 116 (74.8 percent) occurred in the southwestern ADIZ, 25 (16.1 percent) were Median Line crossings, 10 (6.5 percent) were in the southeastern ADIZ, and two each (1.4 percent) were in the eastern and northeastern ADIZs. The overwhelming majority of the 111 dual-zone incursions (82 percent) occurred in the southwestern ADIZ and across the Median Line. That the PLA continues to focus heavily on the southwestern ADIZ should not be surprising. As we have previously argued (see here and here) its location near the strategic “chokepoint” of the Bashi Channel is critical to the PLA’s training and prosecution of its anti-access and maritime deterrence strategies.
Twelve incursions (10.8 percent) occurred in the southwestern and southeastern ADIZs, while four incursions each occurred in the southwestern and eastern ADIZs, and southwestern and northeastern ADIZs. This clearly demonstrates the increasingly tasking challenge faced by Taiwanese defenders.
The 23 triple-zone incursions tend to be large-scale in nature, with an average of 18 sorties per incursion. They also appear to serve various functions. Some of these incursions appear to be shows of force against a U.S. naval presence in the vicinity – typically a U.S. Navy carrier strike group (see here, here, and here). Others were part of Beijing’s response to high-level political engagement between U.S. and Taiwanese officials.
The four quadruple-zone incursions featured UAVs, which have become increasingly frequent participants in the PLA’s operations and training and exercises. Three of the four incursions involved drones circumnavigating Taiwan (see here, here, here), demonstrating the long reach of the newly integrated capabilities.
For example, the “Operation Joint Sword,” the PLA’s encircling drill in response to President Tsai meeting with Speaker McCarthy (see here and here) demonstrated a broadly similar pattern of military responses as we witnessed during Pelosi’s visit. The PLA conveyed a strong message of displeasure about the political engagement yet was measurably less threatening in comparison, again suggesting Beijing’s flexible adjustment of its response.
Nevertheless, the PLA’s responses to Pelosi and McCarthy’s visits to Taipei generated a rather predictable pattern, which can help us predict future behaviors in similar instances.
Then-Speaker Pelosi’s visit to Taipei in August 2022 fundamentally changed the dynamics of the PLA’s aerial incursions into Taiwan’s ADIZ. Most consequentially, the PLA effectively erased the informal boundary formed by the Median Line in the Taiwan Strait by beginning what has become frequent violations of the line. Beijing has become more sensitive and responsive to any enhancement of Taiwan-U.S. relations and the PLA has demonstrated flexibility in its response to U.S. CODEL and other formal visits by adjusting the place and scale of its reaction, including around Taiwan and across the Median Line. In addition, multi-zone incursions that challenge Taiwan’s air defenses at several points simultaneously have become more frequent occurrences.
Despite this “new normal,” most PLA aerial incursions remain low-risk and take place in the southwestern ADIZ as part of PLA’s everyday operations, training, and exercises. There can be no turning back to the pre-Pelosi status quo ante given that Beijing has attained a stronger position and greater flexibility in its toolkit.
In light of these observations, we expect a strong PLA response to Taiwanese Vice President (and presidential candidate) William Lai’s upcoming transit in the United States.