Roger Cohen writes: The interim agreement with Iran, reached in November 2013, has had many merits. Iran has respected its commitments, including a reduction of its stockpiles of enriched uranium and a curbing of production. The deal has brought a thaw in relations between the United States and Tehran; once impossible meetings between senior officials are now near routine.

The rapid spread over the past year of the Sunni jihadist movement that calls itself Islamic State has underscored the importance of these nascent bilateral relations: ISIS is a barbarous, shared enemy whose rollback becomes immeasurably more challenging in the absence of American-Iranian understanding. Allies need not be friends, as the Soviet role in defeating Hitler demonstrated. President Obama’s war against ISIS makes war with Iran more unthinkable than ever. Absent a “comprehensive solution that would ensure Iran’s nuclear program will be exclusively peaceful,” in the words of last year’s accord, the drumbeat for such a war would almost certainly resume. From Jerusalem to Washington countless drummers are ready.

It is critical that this doable deal get done, the naysayers be frustrated, and a rancorous American-Iranian bust-up not be added to the ambient mayhem in the Middle East. The Islamic Republic, 35 years after the revolution, is — like it or not — a serious and stable power in an unstable region. Its highly educated population is pro-Western. Its actions and interests are often opposed to the United States and America’s allies, and its human rights record is appalling, but then that is true of several countries with which Washington does business. [Continue reading…]