The international agreement with Iran did exactly what it set out to do: The policy dramatically curtailed Tehran’s nuclear ambitions and established a rigorous system of monitoring and verification. Once the policy took effect, each of the parties agreed that the participants were holding up their end of the bargain, and Iran’s nuclear program was, at the time, on indefinite hold.

And then Trump took office and abandoned the policy for reasons he never explained.

In broad strokes, Obama set out to use economic sanctions to get Iran to the international negotiating table. That worked, and a breakthrough agreement eventually followed. Trump came to believe he could duplicate the strategy by abandoning the policy, restoring the old sanctions and adding new ones.

This was known as the Republican’s “maximum pressure” campaign, and it was pursued on the assumption that Iran would inevitably return to the negotiating table and accept a new agreement. If Obama’s sanctions led to a landmark deal, the argument went, then maybe Trump’s sanctions could produce an even better deal.

That didn’t happen. Trump’s approach failed......

How Trump arrived at his decision adds insult to injury. One of my favorite stories about the Iran deal came a few months into Trump’s term in the White House, when the president held a lengthy meeting with top members of his team: Secretary of State Rex Tillerson, Defense Secretary James Mattis, White House national security adviser H.R. McMaster and Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford. Each of the officials reportedly told Trump the same thing: It was in the United States’ interest to preserve the JCPOA policy.

The Republican expected his team to tell him how to get out of the international agreement, not how to stick with it. When his own foreign policy and national security advisers told him the policy was working, Trump reportedly “had a bit of a meltdown.”

Soon after, he abandoned the JCPOA anyway — not because it was failing, but because Trump was indifferent to its success.