Anwar al Awlaki has reportedly been killed in an airstrike in Yemen, bringing an end to the life of one of al Qaeda’s most effective recruiters. Awlaki had an especially strong appeal in the West, where an unknown (but surely significant) number of recruits joined al Qaeda’s jihad after viewing his sermons in English.

Awlaki was not merely an online instigator. Most notably, his dossier included ties to the September 11, 2001 terrorist attacks. In fact, one of the enduring mysteries of 9/11 surrounds Awlaki’s precise role in the events leading up to that day.