“There’s nothing boring about this,” Donald Trump said in the White House on 2 March, before commenting happily on the drapes for his new ballroom. Moments like these make me think that the president doesn’t really know why he has taken the US to war. He seems to drop bombs on a whim. He is exercising power for the sake of it, and cares little for coherence or justification. Any hope for a post-war plan does not seem likely considering the blasé way Trump said that possible “candidates” to replace Ayatollah Ali Khamenei had been killed because the mission was...