ONE of the world’s most crucial relationships is going from bad to worse by the day.

China has expressed “serious concern” over Donald Trump’s muscling up to the rising superpower in a series of defiant acts over the past week.

Last week, a single phone call between the President-elect and Taiwanese leader Tsai Ing-wen prompted widespread outrage, with the celebrity billionaire shaking up one of the Asia-Pacific’s most sensitive relationships.

Since then he’s signalled he’s more than willing to confront Beijing, suggesting the United States may drop its “One China” policy, a symbolic understanding that has kept the relationship between the three parties relatively stable for more than three decades.

So what exactly is going on between China and Taiwan, and why was that phone call such a big deal? Here’s a rundown.

WHAT’S THE STORY WITH CHINA AND TAIWAN?

Neither China nor Taiwan see themselves as two separate countries.

But they do have different governments, and the trouble is each side believes itself to be the owner of both territories, in a conflict that dates back almost 100 years.

Quick history lesson: In 1927, a civil war broke out in the Republic of China between the Communist revolutionaries and the Nationalist government.

In 1949, the Nationalists were defeated and fled to Taiwan, which their forces still controlled.

At this point the fighting stopped, but the dispute wasn’t resolved; both sides continued to claim both mainland China and Taiwan belonged to them.

In 1979, the United States switched its recognition from the Taiwan government to Beijing’s. A number of other countries — including Australia — followed suit, and it’s understood no American leader has communicated openly with a Taiwanese president since.

Until Donald Trump came along.

WHY WAS TRUMP’S PHONE CALL SUCH A BIG DEAL?

By openly acknowledging Taipei as separate from Beijing, Mr Trump symbolically backtracked on more than three decades of US-China relations.

Honouring this policy has allowed the United States to make a number of crucial deals with China over the past few decades, on everything from trade and environmental policy to international sanctions.

Associate Professor Jingdong Yuan, who specialises in Asia-Pacific security at the University of Sydney, said it was a poor symbolic move, particularly given he referred to the Taiwanese leader as a “president”.

“Official direct contacts at the highest level between Washington and Taipei are a no-go, something that all three sides are aware and conscious about,” he told news.com.au. “Trump’s phone call breaches this protocol in a significant way.

“His use of ‘President Tsai’ is also a major break from almost 40 years’ practice.”

While it may seem the logical solution is for China and Taiwan to simply split, the reality isn’t that simple.

One of mainland China’s top priorities is keeping Taiwan from ever achieving international recognition as an independent nation.

And that’s a priority Beijing is prepared to go to war over. You only have to look at the controversy over Tibet to see the Chinese government’s fears of emboldening separatism in action.

In a semi-official meeting in 1992, representatives of both Taiwan and China acknowledged that there is “one China”, but each side had its own interpretation of what that meant.

BUT WHAT ABOUT TAIWAN?

While following the “One China” policy is the US’s official party line, its relationship with Taiwan in practice is a little more ambiguous.

For example, the US has been supplying Taiwan with military weaponry since 1979, under the Taiwan Relations Act (TRA).

Dr Yuan said China was aware of this, and begrudgingly accepted it as part of the world order.

“The US maintains close unofficial ties with Taiwan, including arms sales, while working with Beijing on other issues of interest to the US,” he said.

“China opposes every arms sale but largely accepts the fact it cannot stop this, that this is a reality.”

The TRA was created to “help maintain peace, security, and stability in the Western Pacific”, a form of strategic ambiguity that both keeps Taiwan from declaring independence from mainland China, and keeps mainland China from engaging in conflict as a means of unifying both territories.

Basically, it’s a way of keeping peace in the region.

Washington also runs a non-profit centre called the American Institute in Taiwan, which is kind of like an unofficial consulate.

This allows Taipei to enjoy a pretty good working relationship with the United States.

“Beijing is OK that other countries maintain and develop ties with Taiwan as long as the ‘One China’ principle is observed,” Dr Yuan said.

In other words, as long as the US didn’t acknowledge Taiwan as a real country on face value, it could have its cake and eat it too.

While Mr Trump’s phone call may be seen as a show of support for Taiwanese independence, Dr Yuan believes it will only make the region nervous.

“I don’t think Taiwan’s leaders are glowing in the fact this call has taken place,” he said. “If anything, they are also worried about this major departure from past practices that everyone has been used to and more worrisome, the unpredictability of Trump’s remarks.”

According to polling data, most people living in Taiwan are content to maintain the status quo.

A 2008 study by Taiwanese media outlet TVBS tracked the population’s preferences over a period of close to a decade.

From 2000 to 2008, it found there was a consistent majority in support of maintaining the status quo over pursuing independence or reunification, with this option ranging from 42 per cent to 64 per cent.

Pursuing independence was a slightly more favourable option than reunification, which peaked at 23 per cent over the course of the 19 polls.

In a 2013 survey by the country’s Democratic Progressive Party, 77.6 per cent of respondents identified themselves as Taiwanese, while only 10.1 per cent identified themselves as Chinese.

Asked whether Taiwan and China were parts of one country, almost 80 per cent of respondents disagreed.

More than half the respondents said they hoped Taiwan maintained the status quo “forever”, while 22.2 per cent believed that “Taiwan will be unified by China”.

HAS ANY GOOD COME FROM TRUMP’S ATTITUDE TOWARDS CHINA?

China has not taken Mr Trump’s remarks lightly.

Over the past week, the country’s state media agencies have blasted the President-elect, lambasting him as “lacking in experience” and deeming him an “ignorant child”.

In various editorials they’ve suggested his attacks won’t be taken lightly.

The People’s Daily warned that “creating troubles with China won’t make the US ‘great’ again”, while the Global Times warned that China “must confront Trump’s provocations head-on, and make sure he won’t take advantage (of Beijing)”.

Dr Yuan suggested Beijing’s response might be more extreme if Mr Trump’s attitude remained after his inauguration.

Yet he shows no signs of slowing down.

“I don’t know why we have to be bound by a ‘One China’ policy unless we make a deal with China having to do with other things, including trade,” he said in a recent interview with Fox News.

Some critics have welcomed his tough stance. Writing for The Daily Beast, author Gordon Chang said Beijing has gotten away with using intimidating tactics and a frightening image in order to get its own way, and the new American leader was hitting back at that.

“Trump, by calling Taiwan a separate state, indirectly told the Chinese he is not afraid of them, saying, in effect, he does not respect their most important concerns,” he writes.

“He is, in a real sense, starting a new relationship with Beijing, putting everything China has won in the past four decades back on the table.”

But Dr Yuan believes such statements from the President-elect showcase him as both “naive” and “dangerous”.

“The way he trades everything as a commercial transaction demonstrates that he is as naive as he is dangerous; he is challenging China’s core interest and China can never accept this.”

So what’s the way forward? Dr Yuan said if Mr Trump was unhappy with China’s trade and currency practices, he needed to convey them in a way that didn’t use Taiwan as a negotiating tool.

“Deal with them but … don’t use Taiwan as a bargaining chip,” said Dr Yuan.

“Let us just hope he will become more aware of the severity of the consequences of a fracture in Sino-US relations.”

Escalating tensions between China and the United States do indeed spell trouble for the rest of the world, including Australia.

As two of our largest trading partners, the last thing we’d want to do is have to choose one or the other if their relations were to turn increasingly sour.

Aside from that, this ongoing conflict and the threats on either side suggest a US-China war isn’t out of the question.

Now there’s a scary thought.

@GavinDFernando | gavin.fernando@news.com.au