Donald Trump’s newly stated war aim applies an old phrase to a new conflict. The phrase of the hour, “unconditional surrender,” is an echo from American wars of the past, but if the President is serious about pursuing it, unconditional surrender means a substantial escalation of the U.S. military commitment in the week-old Iran war. Moreover, the term may represent a fresh rebuff to the MAGA coalition Mr. Trump created and which sustains him in his second presidency. As a term of the military arts, there likely can be no unconditional surrender without the nation building the President repeatedly disavowed...