At 11 a.m. on Dec. 2, some 60 miles east of Los Angeles, Syed Rizwan Farook and his wife, Tashfeen Malik, stormed into a Christmas party for employees of the San Bernardino county public-health department, where Farook worked. Wearing military-style clothing and black masks, the couple unleashed a barrage of bullets. They killed 14 people, and minutes after the attack, Malik pledged an oath of allegiance to Islamic State on her Facebook page. It was the most lethal terrorist attack in the U.S. since 9/11.
Farooq and Malik were married parents and college graduates. They were solidly middle-class, without criminal records or documented mental-health issues. He was a native-born American, she had recently emigrated from Pakistan, and there was nothing in the basic details of their backgrounds to suggest that they were any special threat.
They were, in short, very much in the social mainstream of American life—and that, perhaps surprisingly, turns out to be typical of homegrown jihadists, whose numbers have been increasing in recent years. In 2015, the FBI investigated supporters of Islamic State in all 50 states, and more than 80 Americans were charged with some kind of jihadist crime, ranging from planning travel to Syria to plotting an attack in the U.S. It was the peak year since 2001 for law-enforcement activity against Americans who had chosen to join a group or accept an ideology whose goal is to kill fellow Americans.
Working with a research team, I have assembled an exhaustive data set of the roughly 300 jihadists indicted or convicted in the U.S. for some kind of terrorist crime since 9/11. Those crimes ranged from the relatively minor—sending small sums to a terrorist group—to murder.