Weng hui-ping wanted to sleep in on her day off. but the taipei yoga teacher was woken up at 7am on monday morning by aircraft screaming overhead. i thought, are the chinese communists here? my house is not close to the airport, it sounded like fighters, she said.

Taiwans defence ministry had a simple explanation: some of its jet fighters and helicopters were practising for taiwans national day on october 10. dont you worry! the ministry said in a statement posted on social media.

But preparations for celebratory flights are not the main reason the countrys air force have been exceptionally busy. china has sharply increased military manoeuvres close to taiwans borders this month, with taipei forced to scramble fighters almost every day during the past two weeks. taiwanese and us officials say it is the worst escalation of military activity in more than two decades.

The military pressure on taiwan is rising alongside chinas growing tensions with the us. as washington strengthens its support for taipei with visits of senior government officials, frequent public praise for taiwan's democracy and arms sales the trump administration is considering a $7bn package beijing is pushing back.

China claims taiwan as its territory and says it reserves the option to seize it militarily. the taiwanese public had grown numb to that 71-year-old threat, after living in peace and de facto independence for decades. but beijings new aggression has raised the alarm in taipei and washington.

Its important for us to recognise that this is not hollow, its real, said chad sbragia, the top china official at the us defence department. and in time, as china builds on its capacities, this will become more intensified and induce more risks.

This week, the peoples liberation army of china has been conducting exercises in five different areas off the coast of taiwan the second time in as many months it has held multiple drills simultaneously.

According to people briefed on operational details, the pla has also stepped up simulations of attacks on taiwans east coast, where taipei has an important missile base and most of its hardened shelters for fighter aircraft.

China

Chinese military aircraft crossed the taiwan strait median line seven days in a row in mid-september. during a visit by keith krach, us under-secretary of state to taiwan and the most senior state department official to travel to the country in more than three decades, the pla flew a total of 37 jets across the line.

Both sides had largely respected the unofficial demarcation until the pla began crossing it frequently in march last year. china asserted publicly that there is no median line in the taiwan strait 10 days ago, obliterating a tacit agreement that helped prevent military incidents.

The erosion ofthe median line will have consequences, and those consequences will very much heighten instability in the taiwan strait, said an official with knowledge of the situation.

The taiwan strait is only 160km wide at its narrowest point. pla fighter sorties in the direction of taiwan over the median line eliminate warning time for the countrys air defences. they also raise the risk that a chinese fighter could mistakenly fly into taiwans sovereign airspace over the main island, which could trigger open conflict.

You have to distinguish between deterrence and threats, said a former top taiwan military official. deterrence would be meant to discourage us from certain moves moves that they would define as pro-independence. threats are the opposite: they are meant to provoke a reaction, to wear us down and to be able to put the blame on us when something goes wrong. what they are doing now are threats.

This leaves no good options for us, the person added. if we react, the risk of incidents rises. if we dont, they undermine our sovereignty.

Taipei and washington are also concerned about the spread of disinformation via social media about alleged us military activity out of taiwan, which chinese hawks have used to argue for punitive military action. washington cancelled its mutual defence treaty with taiwan when it switched diplomatic ties to beijing in 1979, and china has indicated that bringing us military planes or ships into taiwan could be a trigger for a chinese attack.

A potential malign explanation could be that they are trying to construe a casus belli, said a person familiar with the matter.

But many military experts argue chinas moves are an attempt to shake taiwans morale and signal displeasure about closer contacts between washington and taipei.

Chinas not getting ready for something [like invasion], its conducting military diplomacy by using its military forces to try to make political statements on the one hand, and on the other hand, it is trying to put some more miles on taiwanese aircraft, said dennis blair, a retired us navy admiral and former commander of the us pacific fleet. he added that china had never conducted an amphibious exercise targeting taiwan with more than about 1,000 people, far short of the 80,000 troops that would be needed.if you have never practised at a scale above 1,000, in relatively permissive conditions, it would be a fool of a military leader who would say that he has confidence that when he gathers the 80,000, they would be able to not keep out of each other's way, shoot each other, fall off schedule, have a complete debacle which would make the operation fail, he said.