"If you look at the eve of 9/11, the full membership of al-Qaeda was 400 people. But today the people who adhere to bin Laden-ism, to the ideas of Osama bin Laden, are thousands upon thousands. Some estimates put them at forty to fifty thousand." The New Yorker has described former FBI agent Ali H Soufan as the person who came closer than anyone else to preventing 9/11. Today, his time at the agency is portrayed in the Hulu series "The Looming Towers," and he's a leading expert on ISIS, Al Qaeda, and the future of terrorism in an increasingly fragmented world. Spoiler Alert: He does not bring good news.

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