ROBERT SIEGEL, HOST:

When the president laid out his plans to destroy ISIS - or, as he says, ISIL - last night, he compared the effort to U.S. strikes against suspected terrorists in Yemen and Somalia.

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PRESIDENT BARACK OBAMA: This counterterrorism campaign will be waged through a steady, relentless effort to take out ISIL, wherever they exist, using our air power. And our support for partners - forces - on the ground. This strategy of taking out terrorists who threaten us, while supporting partners on the front lines, is one that we have successfully pursued in Yemen and Somalia for years.

SIEGEL: Well, Yemen expert Gregory Johnsen argues that this may be a flawed model. He's the author of "The Last Refuge: Yemen, Al-Qaida and America's War In Arabia." And he joins me on the line from Istanbul, Turkey. Welcome to the program once again.

GREGORY JOHNSEN: Thanks so much.

SIEGEL: Gregory, the target in Yemen has been al-Qaida in the Arabian Peninsula. Recently, you wrote this (reading) The more men the U.S. killed, the stronger al-Qaida seemed to grow.

And as you observe, the U.S. killed some al-Qaida leaders in the process. What's going on?

JOHNSEN: Yeah, so what the president referred to last night is a campaign that the U.S. has been waging, really, since late 2009. The problem, however, is that in Yemen at least, the U.S. has confused killing with winning. So when the U.S. started this campaign in 2009, al-Qaida in the Arabian Peninsula, the group in Yemen, numbered about 200 or 300 individuals. Now we're four years into a bombing campaign, and instead of al-Qaida getting smaller, the group's actually getting bigger. So it's at least three to four times what it was when the U.S. started bombing.

SIEGEL: You relate a sequence of events in the new epilogue to your book that happened last December - al-Qaida attacked a hospital. People there saw security footage on television of a massacre of ordinary Yemenites. And it cost al-Qaida much in the way of public tolerance. Then, a few days later, the U.S. staged a drone attack that mistakenly hit a wedding convoy and everything was back to the way it was, I gather.

JOHNSEN: Yeah, this is a problem that the U.S. has had in Yemen. So really one of the fundamental truths of a war like this is that the side that kills the most civilians loses. Al-Qaida carried out a bloody assault on a hospital and for days, people in Yemen were up in arms. People were talking about what a horror, what a menace al-Qaida was. Then, only a few days later, the U.S. carried out a drone strike that seemed to be based on faulty intelligence. And instead of killing the target, the U.S. actually hit several cars that were in a wedding convoy. And just like that, all of the goodwill that the U.S. had garnered by al-Qaida making its mistake was lost. The difference in this is that al-Qaida apologized for the hospital attack. The U.S. never apologized for the wedding attack. And in fact, it continues to this day to say that it was a clean strike and that only terrorists were killed - a claim that no Yemini believes.

SIEGEL: Is the position of al-Qaida in Yemen analogous to the spread of the Islamic State in Iraq and Syria?

JOHNSEN: Well, there are some similarities. So al-Qaida in the Arabian Peninsula has, like ISIS up in Syria as well as in Iraq, taken over some territory and controlled towns. But ISIS is much bigger. It has much more men and it controls much more territory than does al-Qaida in the Arabian Peninsula in Yemen. So I think one of the problems that the U.S. is going to get into when it starts bombing targets in Iraq more than it has been and even into Syria, as the president suggested last night, is that it's going to be very, very difficult for the U.S. to limit civilian casualties. So in a place like Yemen where the U.S. is using drones, in which drones can stay up in air for hours at a time, in which they can track a single target over days and days, the U.S. still makes mistakes and civilians are killed. What's going to happen when the U.S. is bombing into urban areas in which ISIS is melding in with the civilian population? What we've seen in Iraq and in Syria is that ISIS has grown out of al-Qaida in Iraq. And the group has gotten bigger, it's gotten more menacing and it's become more and more of a threat. So I think the real concern for the U.S. moving forward is how can you tamp down this problem without actually making it worse?

SIEGEL: That's Gregory Johnsen, author of "The Last Refuge: Yemen, Al- Qaida And America's War In Arabia." He was speaking to us from Istanbul. Gregory Johnsen, thank you.

JOHNSEN: Thanks so much, Robert. Transcript provided by NPR, Copyright NPR.