Fifteen years after the September 11, 2001, hijackings, the al Qaeda threat is growing. Al Qaeda has the capacity to attempt a mass casualty attack inside the U.S. and Europe today.

Many assume that al Qaeda is a spent force, especially after the surge of Abu Bakr al Baghdadi’s Islamic State. But they are wrong. Years of erroneous assessments have clouded our vision of an enemy that remains committed to its anti-American cause.