Whatever President Trump's real reasoning, the choice is, at best, incautious and likely a setback for peace. And it should give Americans pause that Mr. Trump has so often mischaracterized the 2015 agreement, formally known as the Joint Comprehensive Plan of Action. First, by saying that, had the U.S. not chosen to lift the sanctions and sign the agreement, Iran would have collapsed, which is foolish considering the purpose of the sanctions was to curb Iran's nuclear program, which they achieved. Second, by claiming that the U.S. "gave" billions of dollars to Iran, when it was merely unfreezing Iran's own assets that were legally due to it. Third, by alleging that Iran is out of compliance (not true), and fourth, suggesting that the deal was weak because the ban on the production of enriched uranium is not permanent — a condition the Iranians would never have accepted. Even so, that doesn't mean Iran was free to make nuclear weapons at some future date; it wasn't.