The first thing to know about the latest controversy over the Iran nuclear deal is that the Obama administration did not pay $400 million in “ransom” to secure the release of three American detainees. Yet that’s the story critics are peddling in another attempt to discredit an agreement that has done something remarkable — halted a program that had put Iran within striking distance of producing a nuclear weapon.

The truth is that the administration withheld the payment to ensure Iran didn’t renege on its promise to free three detainees — a Washington Post journalist, a Marine veteran and a Christian pastor. That’s pragmatic diplomacy not capitulation.

The controversy erupted when The Wall Street Journal reported that the United States delivered $400 million in cash to Iranian officials after Tehran released the American detainees. It has provided an irresistible opportunity for Iran-bashing and Obama-bashing.

What really happened was this: President Obama announced the $400 million payment along with the release of the Americans in January, the day that the nuclear deal was implemented. But the money was part of a separate negotiation over funds the United States has owed Iran since its 1979 Islamic Revolution.