Gruesome public executions served to display and consolidate the power of those capable of inflicting such atrocities upon their opponents. Such spectacles were, as Michel Foucault famously put it, the “ritual destruction of infamy by omnipotence.” In the longer term, however, such public ultraviolence often became self-defeating: As Foucault also noted, the bloodthirsty crowds gathered to witness public executions sometimes developed a dangerous tendency to turn upon the executioners. Awakened bloodlust is difficult to control. Wise leaders eventually learn to dispense with spectacles of ultraviolence; unwise leaders may find themselves eventually dispensed with in their turn.

In the end, however, this strengthens rather than weakens Stern and Berger’s conclusions. “A first step to countering ISIS is to put it in perspective,” they note. “We should not downplay its threat below a realistic level. But neither should we inflate it.” If we exaggerate the threat, characterize “our conflict with ISIS in stark ideological terms,” and allow ourselves to be drawn into an escalating but poorly thought-through series of military confrontations, we risk reinforcing the militants’ apocalyptic narrative “of an all-consuming battle between true believers and apostates.”

Better, they suggest, to contain and undermine the group. While it is impossible to eliminate all jihadist propaganda, anti-Islamic State authorities and companies such as Twitter can, at a minimum, “rais[e] the cost of participation and reduc[e] the reach of radicalizers.” Stern and Berger also urge exposing the group’s vulnerabilities and failures by documenting atrocities against Sunni Muslims and publicizing the poverty and corruption that remain rampant in areas under the Islamic State’s control.