On May 10, a Chinese WZ-10 attack helicopter made headlines for crossing the centerline of the Taiwan Strait. This centerline incursion was the first to occur since September 2020, when then-Under Secretary of State for Economic Growth, Energy, and the Environment Keith Krach visited Taipei to attend the funeral of Taiwanese President Lee Teng-hui (李登輝) and to discuss the launch of the US-Taiwan Economic Prosperity Partnership Dialogue (EPPD). During the September 2020 incursion, close to 40 aircraft crossed the centerline while conducting a live-fire drill. That provocation was promptly condemned by the United States, and no Chinese military aircraft crossed the centerline afterwards—until May 2022. During the latest incident, two KA-28 anti-submarine warfare (ASW) helicopters also flew into Taiwan’s southwestern air defense identification zone (ADIZ), which is the regular location for such incursions.
Beijing generally uses ADIZ incursions to signal its displeasure with Washington and Taipei, in addition to the training benefits of conducting regular sorties in the South China Sea. Centerline crossings, which are very uncommon, are considered a major form of escalation given the proximity to Taiwan. Why did Beijing choose this particular time to make a centerline crossing, and what is its significance? Does it point to a change in Beijing’s approach towards military aircraft flights in the vicinity of Taiwan?
The History of the Taiwan Strait Centerline
The centerline splits the Taiwan Strait down the middle and for decades has been a generally accepted geographic boundary marker between Taipei and Beijing for the purposes of naval and aerial operations. The demarcation was first drawn by the United States in the 1954 Mutual Defense Treaty with the Republic of China (ROC). In that treaty, the US security guarantee extended to Taiwan proper as well as the Pescadores (Penghu), but excluded the outlying islands of Kinmen and Matsu. Additionally, the United States agreed to a buffer zone in the Taiwan Strait, within which US aircraft would not fly; the eastern boundary of that zone later became known as the centerline of the Taiwan Strait.
While the centerline created a buffer between the People’s Republic of China (PRC) and Taiwan, the Taiwan Strait is considered international waters. As such, Beijing has never been obligated to adhere to the US-created line. As Raul Pedrozo wrote for Lawfare in September 2020 after the Krach-related crossing, “China is […] not legally prohibited from crossing the line. However, even though China does not officially recognize the existence of the de facto center line, there has been a tacit understanding on both sides of the strait to respect the unofficial boundary.” That tacit understanding lasted for decades mainly because Taipei—with the support of Washington—had military aviation superiority. It was not in Beijing’s interests at the time to cross the centerline, nor did the PRC have the capacity to pressure Taiwan via aerial incursions across the strait.
However, as the military balance began to shift in Beijing’s favor, the Taiwan Strait became fair game for escalation, signaling, and training purposes. The first reported centerline crossing by a Chinese military aircraft occurred in July 1999 in response to then-President Lee Teng-hui’s statement that relations between the PRC and Taiwan should be conducted “between two countries, at least special relations between two countries.” In 2004, Defense Minister Lee Jye (李傑) described Taiwan’s defense posture regarding the Taiwan Strait in stark terms: “Whenever their aircraft or vessels are approaching the middle line, our aircraft and vessels will be standing by […] Once they keep going east and enter our ‘hunting zone,’ we will take care of them.”
The next crossing did not occur until 2011, in response to US military activity in the region. Following this, there was another long break before the next centerline crossing, which occurred in March 2019. In the years since, crossings have occurred more frequently, with two taking place in 2020: the first in response to a visit to Taiwan by then-Secretary of Health and Human Services Alex Azar, followed by the aforementioned flights following the visit by Keith Krach. Before Krach’s visit, Chinese Foreign Ministry spokesperson Wang Wenbin warned, “China will make a necessary response depending on how the situation develops.” Chinese government officials regularly connect large-scale incursions into Taiwan’s ADIZ with a related “pro-Taiwan” event. Even though Beijing did not, and does not, acknowledge the existence of the centerline—because in Beijing’s view, the Taiwan Strait is only a body of water separating China from one of its provinces—it has generally respected the line as an important delineation point for the two militaries.
Yet, as the PRC military has grown stronger, centerline crossings have become more common, though they still remain rare. In this regard, Beijing perhaps acknowledges the stability of unofficially adhering to the line’s existence. Regularly conducting incursions over the centerline would provide Taipei a reason to the do same, and also potentially for the United States to venture across. Keeping the line in an unofficial state of limbo reduces the risk of escalation from both sides, and reduces the potential for an accident or accidental shootdown.
The Latest Centerline Crossing
After nearly two years of no centerline crossings, the WZ-10 attack helicopter broke the calm. It was the first time that a helicopter crossed the centerline, though it only crossed 0.5 nautical miles onto Taiwan’s side. Notably, it was likely not the recent update to the US State Department factsheet on US-Taiwan relations, which was updated on May 5, that led to the incursion.
The likely reason that the helicopter crossed the centerline was recent US naval activity in the Taiwan Strait. On May 10, the Ticonderoga-class guided-missile cruiser USS Port Royal (CG 73) transited through the Taiwan Strait. According to a US 7th Fleet Public Affairs statement, “The Ship transited through a corridor in the Strait that is beyond the territorial sea of any coastal State. Port Royal’s transit through the Taiwan Strait demonstrates the United States’ commitment to a free and open Indo-Pacific. The United States military flies, sails, and operates anywhere international law allows.” According to S. Rajaratnam School of International Studies Research Fellow Collin Koh, this is the first time that a Ticonderoga-class guided-missile cruiser has made the transit since February 2020, when the USS Chancellorsville (CG 62) did so.
The Chinese People’s Liberation Army (PLA) Eastern Theater Command (ETC) released a statement condemning the US transit and acknowledging the actions that the PLA took in response: “The US has been frequently carrying out provocative acts to send wrong signals to the ‘Taiwan independence’ separatist forces, deliberately stoking tensions across the Taiwan Strait.” According to Senior Colonel Shi Yi, PLA ETC spokesperson, the PLA “tracked and monitored” the Port Royal.
In addition to the US naval transit, the PLA had conducted live-fire drills in the region on May 6-8. A PLA statement on the drills said, “The naval, air and conventional missile forces of the Chinese PLA Eastern Theater Command held drills in seas and airspace to the east and southwest of Taiwan Island from May 6 to 8, in a bid to test and improve the joint operations capability of multiple services and arms.” Notably, Chinese carrier Liaoning participated in the drills to the east of Taiwan. Given its proximity to Japan’s southern islands—several aircraft breached Japan’s air defense identification zone (ADIZ)—the exercise caused Tokyo to scramble escort aircraft. Chinese military drills in this part of the region are meant to demonstrate and test Chinese capabilities during a potential invasion of Taiwan. These goals were especially clear during these recent exercises, which included several missile tests.
It is odd that the US transit would have triggered the first centerline crossing in almost two years. The US Navy has conducted on average one Taiwan Strait transit per month since President Joseph Biden assumed office in January 2021. As such, the Port Royal’s presence is nothing particularly new to prompt such a response from Beijing. A large drill in January 2021 between the US and Japanese navies resulted in 39 aircraft crossing into Taiwan’s southwestern ADIZ, where the PLA normally conducts these operations, without any centerline crossings. Centerline crossings, by contrast, are normally reserved for showing Beijing’s displeasure at trips by senior administration officials, such as those that occurred in August and September 2020. During the September 2020 crossing, the aircraft flew much longer distances along the centerline. The May 2022 centerline crossing is notable in that it happened, but nothing much beyond that. It does not appear to represent a move by Beijing to escalate its ADIZ operations.
While Beijing would never admit it, it is also possible that this crossing was an unintentional accident, and that the helicopter was supposed to turn around before breaching the centerline—especially since it crossed over to Taiwan’s side alone, without escorts by fighter aircraft. During the September 2020 incursion, it was only J-16, J-10, and J-11 fighter aircraft that crossed the centerline. A sole attack helicopter making the crossing is an odd choice. The long delay between the large-scale September 2020 incursion and the solo May 2022 crossing is also puzzling if Beijing hoped to signal its displeasure with the regularly scheduled US naval transit.
To add another layer of complexity to the May 10 crossing, Director of National Intelligence Avril Haines testified before the US Senate Armed Services Committee on that same day to discuss the 2021 Annual Threat Assessment of the US Intelligence Community. The assessment concluded that “Beijing will press Taiwan to move toward unification and will react to what it views as increased US–Taiwan engagement. We expect that friction will grow as China continues to increase military activity around the island, and Taiwan’s leaders resist Beijing’s pressure for progress toward unification.” Given the focus of Haines’ testimony on the threats of Russia and China, it was an even odder choice that May 10 would be the day that Beijing would purposefully send an aircraft across the centerline of the Taiwan Strait.
Whether intentional or not, the May 10 centerline crossing resets the clock until the next time that a Chinese aircraft does so. Perhaps the next breach will shed more light on Beijing’s behavior. Even though Beijing asserted that the sortie was conducted in response to a US naval operation, that rationale has proven to be quite perplexing given the serious nature of centerline crossings and the regularity of US naval transits through the Taiwan Strait. The response does not match the seemingly “offending” behavior.
The main point: The latest Taiwan Strait centerline crossing, carried out on May 10 by a solo Chinese WZ-10 attack helicopter, appears to represent an isolated incident rather than a major escalation by Beijing.