Trump had to crush Iran instead of making deals. He didn't — now he pays the price.

Last April, President Trump scolded Ukrainian President Volodymyr Zelensky on warfare. Trump told Zelensky, "When you start a war, you got to know you can win." That advice was inapt to begin with — Ukraine didn't start the defensive war in which it is now engaged — but it has aged especially poorly. Trump started a war with Iran this...