Trump spent his final day at NATO disputing intelligence that said U.S. strikes on Iran's nuke facilities set the country back only by months.

Mr. Trump had been eager to celebrate his success at NATO and revel in the fact that he had conducted an attack that none of his predecessors had dared to launch. His view was backed up by Mark Rutte, the secretary general of the alliance, who wrote Mr. Trump a private message thanking him for his “decisive action” in Iran.