Japan's new PM said the quiet part out loud on Taiwan and unleashed Beijing's fury

China was already wary about Japan's new prime minister, renowned Beijing hawk Sanae Takaichi, before she weighed in on one of its most sensitive issues: Taiwan.

The saga began in late October when Takaichi was questioned in parliament over how Japan would respond if China conducted a military blockade of Taiwan.

"I believe any action involving the use of force, such as China deploying naval ships, can only be described as a survival-threatening situation," she replied.

The phrase "survival-threatening situation" is a benchmark necessary for Japanese military involvement.

In other words, Takaichi confirmed that Japan may respond to an escalation in Taiwan with military force and become embroiled in regional conflict.

Since then, Beijing has tried to make an example of her.

China issued travel warnings against Japan, calling on nationals to refrain from visiting due to "serious" safety risks.

That resulted in some 500,000 travellers cancelling their plane tickets.

Two Japanese films have also been pulled from the box office and, most recently, China again suspended seafood imports from Japan.

What Takaichi said in parliament wasn't incorrect. The trouble was she that said the quiet part out loud.

"She spoke a truth that the US and Chinese governments were probably aware of, but it was a truth that past prime ministers didn't say aloud," said Jeffrey Hall from Kanda University of International Studies.

"She's shifted the country's official stance."

The sensitive issue of Taiwan

Taiwan exists in a strange grey area.

In many ways, the self-governing, democratic island behaves like an independent country, running its own schools, hospitals, police, military and taxation system.

It overwhelmingly supplies the world's most sophisticated microchips, vital for anything from mobile phones to the most advanced military hardware.

And its geographic position forms part of a wall with Japan and the Philippines, both US allies, that impedes China's access to the Pacific Ocean.

But Taiwan is a legacy from the Chinese civil war, a final bastion of the Nationalists that lost the mainland to the communists.

Since then, the Chinese Communist Party has regarded Taiwan as a breakaway province that must be brought back into the fold, with force if necessary.

Governments in the US, Japan, and other like-minded nations navigate the issue of Taiwan's freedom with "strategic ambiguity", refusing to make clear if they would respond to Chinese action on the island with military force.

The US does, however, provide Taiwan with the "means" to defend itself, under the Taiwan Relations Act, and maintains unofficial defence relations with the island.

"In the US, there's debate about this," said Professor Stephen Nagy, an international relations expert from the International Christian University in Tokyo.

"Should we drop the strategic ambiguity and just say, 'Taiwan matters for everybody'? If there's a fight over Taiwan, we're going to be there."

The significance of the PM's comments

The US has previously warned China is readying its military to be ready to invade Taiwan in 2027.

If the United States did get involved militarily with a Taiwan conflict, or "contingency", there would be an expectation of support from its allies, particularly Japan, even if it was logistical support rather than direct military engagement.

Japan, after all, hosts the largest contingent of US forces outside continental America.

It's also built military bases on islands near Taiwan, purchased Tomahawk missiles capable of striking mainland China, and Ms Takaichi has hastened the country's military spend to reach 2 per cent of GDP by next year, instead of 2028.

So, Japan, like other nations, is preparing for a possible conflict with China over Taiwan.

But this is the quiet part.

Intervention over Taiwan is openly discussed and debated in academic circles but not openly acknowledged by world leaders.

Instead, presidents, prime ministers and foreign ministers routinely call against any "unilateral attempt to change the status quo".

Takaichi's comments signified a shift away from the usual ambiguity.

"She wanted to first distinguish herself," Professor Nagy said.

"I think there's a feeling in Tokyo that the Chinese economy is in deep, deep, deep trouble.

"And their negotiation position vis-à-vis the United States is getting weaker and that there was some space to have a stronger position."

It prompted Beijing to respond with fury.

'They don't like Takaichi'

In a now-deleted post, China's consul general in Osaka responded that "the dirty head that sticks itself in must be cut off", a seemingly direct threat to the Japanese Prime Minister.

More recently, China's Defence Ministry spokesman Jiang Bin said any interference over Taiwan would result in Japan's "crushing defeat".

"They [China's government] don't like Takaichi," Professor Nagy said.

"They knew she was going to be stronger on China.

"They watched her first diplomatic performance and the take homes with President [Donald] Trump. I think they were horrified, not because she did a bad job, but actually with how well she did. Much beyond expectations."

Professor Nagy said Beijing's "blatant economic coercion" is reminiscent of the economic coercion China used against Australia, after then prime minister Scott Morrison called for an inquiry into the origins of COVID-19.

He said the lesson was to acknowledge the importance of China to Japan, while building resilience and diversifying trade.

"It's in their face again that they have to build resilience and deterrence," he said.

For now, Takaichi has made it clear she will not be repeating the comments she made on Taiwan.

But, given her reputation as a hawk, it's widely expected she will not back down either.