MARY LOUISE KELLY, HOST:

In Tehran, on a reporting trip earlier this year, my producer and I walked amid throngs of Iranians in the streets. Some were weeping. Some carried red flags with the words, hard revenge. Well, this was at the funeral procession for the first towering figure in Iran's national security establishment to be assassinated this year - Gen. Qassem Soleimani back in January. And I thought about those red flags, about the calls for revenge these last few days as news broke of another assassination, this time of Iran's top nuclear scientist and this time on Iranian soil in a mountain town outside Tehran. Iran has blamed Israel for the attack, an accusation a U.S. official told NPR appears to be true. Israel has neither confirm nor denied it. But to consider what revenge might look like, what the risks and opportunities are for Iran, we turn to Abbas Milani. He directs the Iranian studies program at Stanford.

Professor Milani, welcome.

ABBAS MILANI: Thank you for having me.

KELLY: Start with the question of whether revenge, whether retaliation for the death of this scientist, Mohsen Fakhrizadeh - whether that is a given. Do you believe Iran has to do something?

MILANI: Iran, I think, has to do something because by their own rhetoric and their rhetoric of revenge, they have to make a response. But I think they also recognize - virtually everybody - that a response at this time might get them into a full confrontation with Israel, assisted maybe with Saudi Arabia, eventually, maybe even the United States. And I don't think they want that. So I think whatever revenge they will try to make, I think it will be later, and it will be more symbolic. They need to have peace at this time. They can't afford a war.