“It’s horrible. We still don’t know what happened,” said Ali Soufan, one of the lead FBI counterterrorism agents whom the CIA kept in the dark about the movements of the future Al-Qaeda hijackers. To Soufan and many other former national security officials, the unanswered questions about the events leading up to the September 11, 2001, attacks dwarf those about the assassination of John F. Kennedy, because “9/11 changed the whole world.” It not only led to the invasions of Afghanistan and Iraq, the fracturing of the Middle East and the global growth of Islamic militantism but also pushed the U.S. closer to being a virtual homeland-security police state.