So why should a phone call between Donald Trump and Tsai Ing Wen matter?

Trump has spoken to Taiwan President Tsai Ing Wen. Photo / AP

1 It could have been a mistake

US President-elect Donald Trump's inexperience in foreign affairs was an issue during the election campaign. Last week he spoke in glowing terms to Nawaz Sharif, the leader of Pakistan, a country which has a tense rivalry with India. Trump also invited the Philippines President to the White House and praised his anti-drugs war which has seen thousands killed. Now he has broken a 37-year protocol about Taiwan's status, conducting a phone call with President Tsai Ing Wen. The US broke diplomatic ties with Taiwan in 1979 and does not recognise its sovereignty, though (as Trump pointed out in a tweet) it sells arms to the island. Christopher Hill, a former assistant secretary of state for East Asia under George W. Bush, tweeted: "This is an example of winging it in the extreme. Hope Trump doesn't feel he has to double down on this judgment error". Other countries, including North Korea, will be sure to test Trump's judgment as president. Russia and China could see his presidency as a chance to expand their spheres of influence. Asia is already troubled with territorial disputes and arms buildups, and countries bordering Russia in Europe must be nervous.

2 It went against China

The US has to cooperate with rival major powers China and Russia on a range of issues, such as climate change. The status of Taiwan is something that is important to Beijing - which insists on a "one-China" policy. China's initial move was to downplay, with Foreign Minister, Wang Yi, describing it as a "petty action" by Taiwan that will not change the policy. Former State Department official Emily Parker tweeted: "Just going to throw out there that China might be sophisticated enough to understand that this wasn't deliberate policy shift." Writing in the New Yorker, Evan Osnos said: "Whether it says it or not, China will regard this as a deeply destabilising event ... because it reveals the incoming presidency to be volatile and unpredictable. In that sense, the Taiwan call is the latest indicator that Trump the president will be largely indistinguishable from Trump the candidate". If it was a deliberate move - and a number of Republican officials quickly got behind Trump, perhaps suggesting planning - it hints at a new attempt to counter Beijing's power in Asia. There are a number of anti-China hardliners, such as former US Ambassador to the UN John Bolton, around Trump. Obama adviser Dan Pfeiffer is sceptical, tweeting: "There can be a lot of takes of the Trump Taiwan call, but the worst are the smart Republicans trying to pretend this was part of a strategy." Ari Fleischer, a former press secretary to George W. Bush, tweeted: "Uh-oh. I wasn't even allowed to refer to the gvt 'of' Taiwan. (I could say gvt 'on' Taiwan.) China will go nuts." But he added: "So long as Trump called knowing it would change the status quo, I'm fine with it. I hope it was by design."

3 It breaks a tradition

Recognition of the one-China policy has allowed the US, China and Taiwan to co-exist relatively peacefully for decades. Trump's campaign rhetoric was to shake-up scripted norms. As Jeet Heer of the New Republic pointed out on Twitter: "Trump wants to replace bipartisan internationalist consensus with policy of bilateral deal making. He needs to break up existing system." This may just be the start of a chaotic four years. Writing in Politico, former Clinton adviser Philip Gordon says: "The risk with Trump is less that he will pursue a grand strategy that causes problems than that he will have no coherent strategy at all." But Gordon argues that: "When it comes to the big, controversial foreign policy decisions a US president needs to make, he will have to grapple with the reality that some degree of caution and pragmatism may be required". Since the election Trump has only had a few intelligence briefings and reportedly hasn't met State Department officials. He has yet to appoint a Secretary of State. That decision seems particularly crucial now.

China has put pressure on Taiwan over the new incident. Photo / AP

4 It inserts uncertainty

Longstanding norms of diplomacy allow countries to predict other nations' behaviour and plan, and to fall back on that clear framework where necessary. If there's uncertainty there's a sense that anything goes. And countries will use whatever new plays Trump comes up with against each other. China has put pressure on Taiwan over the new incident. Democratic Senator Chris Murphy tweeted: "These are major pivots in foreign policy w/out any plan. That's how wars start." Osnos writes: "Trump has also shown himself to be highly exploitable on subjects that he does not grasp. He is surrounding himself with ideologically committed advisers who will seek to use those opportunities when they can. We should expect similar moments of exploitation to come".

5 It could be tied to Trump's business interests

The Guardian reports that weeks before Trump's Taiwan phone call "a businesswoman claiming to be associated with his conglomerate made inquiries about a major investment in building luxury hotels as part of the island's new airport development". ABC News reports that the Trump Organisation says the company has no plans to expand in Taiwan and that "rumours" to the contrary are false. Trump's daughter Ivanka, who will be involved in running her father's business, attended a meeting between Trump and the Japanese Prime Minister Shinzo Abe. The New York Times reported that a month before the election, Philippines President Rodrigo Duterte named Trump's business partner in Manila, Jose Antonio, a "special envoy" to the US. There are concerns about potential conflicts of interest between Trump's business empire and US foreign policy. There's potential for both Trump and foreign governments to make use of those links.