A longtime journalist and CNN terrorism analyst, Peter Bergen is one of the few Western journalists to have interviewed Osama bin Laden. In his latest book, The Longest War, he surveys the wars in Iraq and Afghanistan from the perspectives of the U.S.—and al-Qaeda.

What was the genesis of this book?

We've had a lot of histories of what the U.S. has been doing in the war on terrorism, but not so many that try to integrate what both sides were thinking. Whether I succeeded is another matter, but histories of WWII only told from the perspective of FDR would be curiously one-sided.

What is the result of integrating the view of both sides?

Both sides have made strategic errors. Luckily, ours have been less damaging, but they haven't been insignificant, whether it was losing the war of ideas through coercive interrogation measures in Guantánamo or invading Iraq and shortchanging Afghanistan. On the other hand, al-Qaeda and the Taliban have made egregious errors, particularly al-Qaeda attacking on 9/11, which turned out to be a kamikaze mission for the organization and its Taliban hosts.

The assessment of 9/11 as an error for al-Qaeda may surprise some readers, but you describe the backlash against it in the Muslim world and argue that the greatest ideological threat to al-Qaeda comes from the Muslim world itself. Do you see that continuing?

I think it will. In the DNA of these groups are the seeds of their own destruction because they're not going to engage in normal politics. Hezbollah and Hamas share some ideological similarities to al-Qaeda, but they're also engaged in real-world politics and they're willing to make compromises, whereas al-Qaeda isn't really giving anybody anything. There are no al-Qaeda schools or social welfare services, the kinds of things that more nationalist jihadist movements involve themselves in. The flip side is that these groups can still do all kinds of damage. The Baader-Meinhof Gang was a very small group of people with very little public support that still inflicted tremendous damage on German society. So al-Qaeda is losing public support, but I don't think that's a deal killer for them. It's always been a small organization.

Historian Chalmers Johnson's books, including his latest, Dismantling the Empire, speak of imperial overreach and the untenable nature of military presence around the globe. Do you share this concern?

I agree that we're wasting a lot of money on some aspects of our military. But maintaining some kind of military presence in Afghanistan for some period of time, well past 2014, I think (a) will happen and (b) is in our interest and in the Afghan people's interest. Afghans are very conscious of the fact that we abandoned them in 1989, after helping them defeat the Soviets—neither Afghanistan nor Pakistan want us to just pull out. They may want us to take more of a backseat, and that's what we're going to do, but we're going to be involved for a long time.