BRUSSELS — In Vienna last week, the signers of the 2015 Iran nuclear deal came together with what would appear to be a simple task. They wanted to restore compliance with an agreement that puts strict controls on Iran’s nuclear enrichment, to ensure that it cannot build a nuclear weapon, in return for the lifting of punishing economic sanctions.
Both Iran and the United States insist that they want to return to the deal, known as the Joint Comprehensive Plan of Action. But nothing about the meetings is simple.
The first sessions went well, with working groups established to try