SINGAPORE – Chinese military warplanes made yet another foray into Taiwan’s air defence identification zones (ADIZs) on Tuesday (June 21), prompting the island to scramble jets to warn away 29 Chinese aircraft.

It was the third largest Chinese aerial incursion this year around Taiwan. The largest drill to date this year featured 39 aircraft on Jan 23, while 30 Chinese planes were reported entering the island’s ADIZ on May 30.

Tuesday's exercise was ostensibly a show of force in the face of a US aircraft carrier in the region, particularly in the wake of the US' recent rejection of China's claim on the Taiwan Strait in what Beijing deems another challenge to its "one-China" policy. 

What is an ADIZ

An ADIZ is an aerial zone comprising a country's or territory's sovereign airspace and a larger buffer belt over international waters. It is unilaterally declared by a country or territory in the name of national security, and foreign aircraft are required to seek permission before entering this zone.

An ADIZ is different from territorial airspace which, according to international law, corresponds to a state’s territorial waters that ends 12 nautical miles from its coastline. An ADIZ can extend far beyond territorial airspace, and sometimes overlaps the ADIZs of neighbouring states.

Because of its larger size, an ADIZ gives a state or territory some time to scramble its jets to intercept intruding aircraft.

The US declared the world’s first ADIZ during the early Cold War era in 1950 to protect against surprise attacks by Soviet Union bombers. Other places with ADIZs include China, Japan, South Korea and Taiwan.

If ADIZ boundaries are respected, the zone will help to reduce the risk of accidental collisions and the need to send warplanes to inspect intrusions.

In 1960, for example, the Soviet Union did not have an ADIZ and the resulting confusion led to an American spy plane being shot down over international waters.

Why it can be contentious

Demarcating zones can become contentious, particularly when one country’s unilateral declaration overlaps with that of another nation.

For example, in 2013, Japan and China separately declared ADIZs in the East China Sea that covered the disputed Senkaku or Diaoyu islands.

In a testimony to the US House of Foreign Affairs, Dr Peter Dutton, a director of the China Maritime Studies Institute at the US Naval War College, said China sought to use its 2013 declaration to assert its legitimacy to operate within the ADIZ, an act seen as provocative by Japan given the contest over the territory.

Retired Indian fighter pilot PI Muralidharan also said in a report for think tank Institute of Peace and Conflict Studies that an ADIZ does not equate to territorial boundary, nor would it justify interfering in another state’s aerial navigation rights, especially in peacetime.

Meanwhile, Taiwan’s ADIZ, established in 1953, covers most of the Taiwan Strait and extends into parts of Fujian, Zhejiang and Jiangxi in the mainland. But defence analyst Gerald Brown said Taiwan does not record flights over the mainland as aerial incursions, only doing so when a Chinese aircraft leaves its airspace and enters Taiwan’s ADIZ, often by crossing the median line of the Taiwan Strait.

Why it matters to China

China does not recognise the median line. Last year, foreign ministry spokesman Wang Wenbin also claimed Taiwan as an “inalienable part” of the mainland, flatly rejecting the notion of a line dividing the strait.

Defence Minister Wei Fenghe reiterated Beijing's “one-China” stance at the Shangri-La Dialogue in Singapore earlier this June, asserting that “Taiwan is first and foremost China’s Taiwan”. He said China will not hesitate to “fight at all costs” to defend all of its sovereignty and territory.

The Chinese and American defence chiefs, Mr Wei and Mr Lloyd Austin, had their first in-person meeting - described as a "good start" - at the dialogue. But barely two weeks later came China's latest aerial missions into Taiwan's ADIZ.

The Chinese People’s Liberation Army (PLA) has been carrying out these sorties into Taiwan’s ADIZ seemingly to display its air force's prowess.

According to Chinese military experts cited by the Global Times on Wednesday (June 22), China’s latest exercise included three separate groups of aircraft for the specific purposes of countering possible interventions by US aircraft carriers that were reportedly operating in the nearby Philippine Sea recently, as well as to “seize air superiority”.

Aerial drills were performed by an electronic warfare aircraft, an electronic intelligence plane and six bomber jets in one group, and an aerial refuelling aircraft, two early warning planes and 17 fighter jets in another.

A third group comprising anti-submarine warfare aircraft patrolled the Taiwan Strait to observe any “hostile underwater and surface activities” and to “share intelligence” with its PLA units, said an expert who was not named.

The analysts characterised the combination of aircraft in Tuesday’s drill as “combat-oriented”, demonstrating the PLA’s readiness to engage Taiwan independence secessionists and foreign interference “by force” if needed.

There are also fears that China may declare an ADIZ over the disputed South China Sea. It has laid claim to nearly all of the waters, angering others with competing claims - Taiwan, Vietnam, the Philippines, Malaysia and Brunei. 

Why it matters to Taiwan

Taiwan Foreign Minister Joseph Wu said on Wednesday the large-scale exercise by the Chinese military showed China’s military threat is “more serious than ever”.

Taiwan has labelled China’s repeated flybys as “grey zone” warfare. Taiwanese military expert Lu Li-shih said the PLA’s planes could have been deployed to wear out Taiwan’s defence forces by forcing them to repeatedly scramble and intercept encroaching planes, and also to gather intelligence on its response procedures.

Such missions by Chinese aircraft have become a common occurrence over the past two years. The island has seen at least 547 incursions by PLA planes so far this year. There were 962 sorties recorded in the whole of last year.

According to its Ministry of National Defence, Taiwan’s defence forces had to scramble 2,972 times to intercept Chinese aircraft in 2020 at a hefty cost of NT$25.5 billion (S$1.24 billion).

Taiwan International Strategic Study Society chairman Wang Kung-yi said PLA planes not intercepted could take just 200 seconds to reach Hsinchu, the island’s closest point to the Taiwan Strait’s median line.

According to the Institute of Peace and Conflict Studies, China’s actions may lead to miscalculations, or worse, aerial clashes with the “potential to trigger wider conflict”.

Taiwan’s Defence Minister Chiu Kuo-cheng predicted last year that China could be ready to mount an invasion of the island by 2025.

What may happen

China may continue racking up aerial incursions into Taiwan’s ADIZ should Beijing's relations with Taipei and Washington remain frosty. 

The PLA said last month it had conducted an exercise around Taiwan as a “solemn warning” against its “collusion” with the US.

That came days after President Joe Biden said that the US would get involved militarily if China were to attack Taiwan, although the White House tried to walk back his remarks.

And while top US diplomat Antony Blinken last month affirmed his country’s commitment to its “one China” policy, he also called the PLA “provocative” in the same speech outlining the Biden administration’s approach towards China.

Mr Wang, China’s foreign ministry spokesman, this month accused the US of “backpedalling” on its commitment by increasing weapons sales to Taiwan and increasing “official interactions” with Taipei. A week later, China conducted its latest aerial sorties into the island’s ADIZ.

Beijing has also mounted bouts of aerial drills into Taiwan’s ADIZ to coincide with special occasions such as China’s national day last year on Oct 1, and could repeat those moves this year.

Mr Biden said on Tuesday he plans to talk to his Chinese counterpart Xi Jinping as he mulls over lifting some tariffs imposed on Beijing by his predecessor Donald Trump. 

But that meeting's impact on defence relations is unlikely to improve based on their previous exchange last November. 

Both presidents had shared views on "everything under the sun, but announced no decisions or policy steps", said China expert Scott Kennedy at US-based think tank Centre for Strategic and International Studies after the talks. He added that both sides agree on needing stability in US-China relations, but "don't agree about how to get there".

This year, the US has imposed a diplomatic boycott on the Beijing Winter Olympics, and enforced a ban on products made in Xinjiang over alleged human rights abuses. Beijing has decried the "politicising of sports" and said forced labour allegations are a pretext for the US to destabilise China's development.