China’s leaders have been recognised as the ultimate pragmatists. In the past few decades they have been able to work across the Middle East, when most others in the region have had to choose between enemies and friends.

Some have called this approach amoral, and it is certainly motivated by an intense sense of what best serves China’s interests. In recent decades, in international affairs, that has been securing resources, finding markets to sell to, acquiring and developing technology and know-how, and ensuring that China has a benign and largely stable environment around it.

Even the recent activism over the South and East China Seas’ maritime borders does not disprove this narrative. China has worked carefully to push, test and raise questions in its immediate neighbourhood, but it has largely operated in signs and symbols, keeping clear of any real risk of military action.

Donald Trump’s US election win surprised Beijing as much as it did the rest of the world, and it knows as little about the new president-elect as most other countries on the planet do. It too had anticipated dealing with a Clinton presidency.

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Trump made fierce comments about China’s economy during his spectacularly ill-tempered campaign. His most provocative statement and actions since then have been on Taiwan, whose president, Tsai Ing-wen, he spoke to on the phone in early December. But even on this issue there are questions over whether this is not part of a campaign more focused on trade than anything else.

Taiwan’s status is one of the few international issues that the Chinese care markedly more about than the Americans.

Is it something that the US and China can bargain over? At the moment, it is hard to read Trump’s intentions. Beyond this, there are questions about whether Trump can do much about many of his (often contradictory) statements about getting a fairer economic deal for the US. The idea that a new kind of trade deal with China would bring jobs back to the United States was one of the most powerful and consistent points that he made.

But what kind of jobs would these be, and how could they come back?

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Even Chinese manufacturing is slipping away to other, cheaper, places. And do Americans really want low-end manufacturing jobs to spend their careers in?

Trump could be fiercer on Chinese currency valuations. But in the end, this is an old story, and China has already made many corrections and adaptations on this. So it is hard to see this getting very dramatic very quickly, if at all.

One thing Trump has been clear about is scrapping the Trans-Pacific Partnership, the China-excluding trade deal between 12 nations in the Americas and the Asia-Pacific. China would happily see that deal bite the dust – as it neither was part of it nor supported it – and has already started moves on its own Asia-wide free-trade deals to fill the space left by the US.

But as they start to engage with the new US president, Chinese leaders will have questions in their minds.

Primarily, they will watch the Taiwan issue closely. Trump speaking as president-elect is different from him speaking when he’s actually in the hot seat after January 20. If he continues his hardline approach then, there will be diplomatic bad blood.

For Chinese President Xi Jinping ( 習近平 ), progress towards a long-term framework for reunification would be a huge achievement, and put him in the history books. This would not involve military intervention, just constant economic and diplomatic pressure. A less intense, less involved US would suit Xi fine in this ambition, and clear away one of the great inhibiting factors. The question is whether Trump is actually working towards a deal like this, and what his bottom line might be.

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More generally, America’s lessened presence in the Asia-Pacific moves China a substantial step closer to exercising the kind of regional dominance it evidently places at the heart of its foreign policy aspirations. China doesn’t want global reach and responsibility. But it does want regional power, which an isolationist Trump presidency would bring nearer.

In all plans, of course, there are potential spoilers. For China, the most prominent of these is North Korea.

In John Garver’s comprehensive history of Chinese foreign policy since 1949, China’s Quest, Garver shows how in the early 1950s, when China had the real opportunity to invade Taiwan and achieve a quick reunification, the Korean War distracted it, drawing the US into the Korean peninsula, which it has never left. China’s opportunity disappeared.

There is a real worry that the leadership in Pyongyang will repeat a pattern from the past and welcome the new president in with some provocation – another nuclear bomb test, or something even more dramatic. In that case, the Trump administration would face a truly existential threat and have to take action.

For the Chinese, whose default on this is to stall, strive for the status quo, and do nothing, Trump’s impetuousness, inexperience and general ignorance of foreign affairs could lead to any of a number of decisions that could be disastrous, for China, the region, or the US. In this area, the Trump era – with its lack of clarity and definition – is extremely worrying.

And, for China, dealing with someone so hard to second-guess will be one of the greatest foreign policy challenges America has ever presented.

Kerry Brown is a professor of Chinese politics and director of the Lau China Institute at King’s College London