After more than 20 months of negotiations, a landmark deal was reached Tuesday between world powers and Iran that curbs Iran’s nuclear program in exchange for the easing of economic sanctions. The deal reduces Iran’s stockpiles of enriched uranium and the number of its centrifuges by two-thirds. It also prevents Iran from producing weapons-grade plutonium. 

A new book, Unthinkable: Iran, the Bomb, and American Strategy by author Kenneth Pollack, explores the advantages and potential consequences of different foreign policy approaches. Pollack joins us to discuss the book. Read an excerpt.

Though the historical handshake between President Barack Obama and Iranian President Hassan Rouhani didn’t happen at the United Nations luncheon today, there’s already speculation another opportunity may be on its way, and relations between the two countries could continue to thaw. We talk with Middle Eastern political expert, Marvin Zonis. View a timeline of U.S. and Iranian diplomatic relations.

Diplomacy is being put to the test in Iran. Tightened sanctions and threats of war are making the situation even more tense. We explore the details of the standoff.