Taiwan raised the alarm last month over a record number of Chinese fighter jets crossing the unofficial border between them, Beijing said that line did not exist.

Another escalation in Chinese war games occurred with the 103 fighter jets China flew near Taiwan, 40 of which entered the island’s Air Defence Identification Zone (ADIZ).

China, which has long claimed Taiwan, has repeatedly rehearsed encircling the self-ruled island with fighter jets and navy ships in the past year. With China vowing to “reunite” with Taiwan, the military drills have taken on an especially menacing tone.

Manoeuvres have so far avoided an invasion and remained in the grey zone, which is military speak for a middle ground between war and peace.

As a result, Taiwan has become a tinderbox in what has become a volatile US-China relationship, and analysts say Beijing is using grey zone tactics to control Taipei without firing a single shot.

An objective of grey zone warfare is to weaken an adversary over time, and that is what China is trying to do with Taiwan.

China is regularly crossing Taiwan’s ADIZ to test how far Taipei will go to reinforce it, says King’s College London professor Alessio Patalano.

The Chinese have routinely scrambled fighter jets to warn off Taiwanese aircraft in its ADIZ, which can strain Taiwan’s resources in the long run, Prof Patalano said.

One advantage of the drills is that they allow China to test its own capabilities, such as force coordination and surveillance, according to analysts. In addition, they fit China’s pattern of normalizing increasing levels of military pressure against Taiwan in order to test its defences and international support.