Trump’s meeting with Chinese President Xi Jinping reportedly included this exchange:

He said they hit it off during their first discussion. Mr. Trump said he told his Chinese counterpart he believed Beijing could easily take care of the North Korea threat. Mr. Xi then explained the history of China and Korea, Mr. Trump said.

“After listening for 10 minutes, I realized it’s not so easy,” Mr. Trump recounted [bold mine-DL]. “I felt pretty strongly that they had a tremendous power” over North Korea,” he said. “But it’s not what you would think.”

In fact, Trump was one of the few to believe that China “had a tremendous power” over North Korea to get them to do whatever Beijing wanted. That he “felt pretty strongly” that this was the case shows how little he understood about the issue. While it is good that Trump can be made to understand that his simplistic, uninformed views on foreign policy issues are deficient, it’s also true that we don’t want the president to be in a position where he is learning (possibly for the first time) about complicated subjects from the head of another government.

This anecdote points to Trump’s own woeful lack of preparedness on this and other foreign policy issues, and it also shows how susceptible he is to being manipulated by other leaders who are far more practiced and proficient in discussing these things. The trouble isn’t just that Trump doesn’t seem to be adequately briefed in advance, but that any briefings he may have received have no effect:

Several diplomats said that early Trump meetings with Merkel, Japanese Prime Minister Shinzo Abe and British Prime Minister Theresa May also raised concerns over Trump’s unorthodox style of working largely without detailed notes and speaking off the cuff.

“He doesn’t have a paper in front of him. . . . It’s up to the visitor to declare the agenda,” one said. “He just sits there. It’s like you are in a bar, and you just start talking to him.”

Whatever else one wants to say about this, it suggests that most meetings between Trump and foreign leaders are not going to be very productive, or insofar as they are productive the agenda is going to be shaped to a large degree by the foreign leader.