Donald Trump complained to his top aide, then Chief of Staff, John Kelly, that he wanted top US generals, including retired military figures, to show him absolute, unconditional loyalty, while pointing specifically to Nazi Germany as an example. In a bizarre exchange described by reporters for The New Yorker and The New York Times in an upcoming book, Mr. Trump is said to have asked his top aide, who was himself a four-star general in charge of U.S. Southern Command, “[W]why can’t you be like the German generals?” A stunned Mr. Kelly reportedly replied, “Which generals?” to which Mr. Trump...