Faced by the collapse of his only diplomatic ‘achievement’ and worried about his support at home, the president could go rogue, North Korea is fast emerging as the definitive example of how Trump takes a pre-existing international crisis and makes it worse. In a letter delivered two weeks ago, Kim reportedly threatened to resume nuclear weapons and missile tests, because Trump had reneged on understandings reached with Kim and subsequently zig-zagged to a harder position. Trump’s over-reaching, and subsequent reneging, is likely to enrage the Pyongyang regime, where hardliners are already crying betrayal. Kim himself may feel humiliated by Trump’s failure to fulfil dangled promises about a peace treaty or formal diplomatic recognition. The result could be a redoubling of the north’s efforts to build weapons of mass destruction and a rapid reigniting of regional military tensions.