The North may believe that Trump is an easy mark for the latest iteration of this approach. The president is not given to extensive preparation or attention to detail, and his recent White House meetings on immigration and guns demonstrate a negotiator who is eager to tell his interlocutors what they want to hear, even if it is counter to his administration’s policy. Trump will be under pressure from South Korea and from his State Department to be conciliatory, and the temptation to get an agreement, any agreement, to wave around as an against-the-odds diplomatic achievement will be considerable.

If such a meeting comes off — and there is still some significant chance that it won’t — the U.S. will have to be carefully prepared. It will have to resist playing by North Korea’s rules in terms of venue and parameters, be willing to bring up items that are a surprise to the North Korean side, and be ready to declare the negotiations a failure without notice, accompanied by new punitive measures. And do all this while engaging in alliance maintenance, knowing that the North desperately wants to split us from the South.