Bangladesh, June 26 -- nly a few days ago, President Donald Trump was calling Iran's leaders "scumbags" and "crazy bastards." He described Supreme Leader Ali Khamenei as one of the world's most evil men and threatened devastating military retaliation.

Today, the same president has signed a memorandum of understanding with those very leaders in the hope of ending nearly half a century of hostility between Washington and Tehran.

Whether the agreement ultimately succeeds or fails, the reversal is extraordinary.

Language of confrontation

For forty-seven years, the United States and Iran have viewed one another almost exclusively through the language of confrontation. Diplomatic relations disappeared after the 1979 Islamic Revolution. Eco...