China is the biggest foreign patron of Cambodia, where Mr. Xi concluded a tour of Southeast Asia. But the region also needs to curry favor with President Trump.

Mr Trump’s breezy style has long disconcerted China’s leaders. In the spring of 2017 he called Mr Xi so often to ask for help with North Korea that Chinese envoys eventually delivered a discreet message to American contacts. Mr Xi is “not our North Korean desk officer”, they pleaded: let underlings handle most of this.

The Trump team’s strategy, to the extent there is one, has been marked by impulsiveness. But what is China thinking? To shed some light on that question, I spoke with Dan Wang, a research fellow at the Hoover History Lab at Stanford University,