As a young and ambitious real estate developer in New York City of the late 1970s, Donald Trump had little love for an American president, Jimmy Carter, who seemed to him timid and indecisive. This annoyance turned to rage and mockery when the new Islamic state took 52 American hostages they would end up holding for more than a year. To the New York businessman, the idea of spending more than 400 days talking to a hostile regime that labeled the U.S. the “great Satan” represented unforgivable incompetence. The United States, he knew, possessed both the military and economic tools needed to bring Iran to its knees. None of them were used. There was a botched rescue attempt in April 1980, when the hostages had already been in captivity for half a year, but little else was done because the Cold War still raged and neither the U.S. nor Israel could take wider liberties, at the risk of Soviet intervention. Carter could not assassinate Ayatollah Ruhollah Khomeini in the way recent attacks have eliminated his successor. Thus the circle is now squared, from old impotence to big strike force. The real estate developer–turned president has evolved into a minor Shiva, a small destroyer of worlds. The impotent Carter legacy has been set aside. As have been the efforts of Barack Obama, who reached a tortuously negotiated 2015 nuclear deal with Iran that this president repeatedly described as “horrible.” Mr. Trump craves the role of hero and liberator — both now in the offing — no historical strings attached.