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Why the Nashville bomber warned people to evacuate

Terrorists often want to persuade civilians to their side — while luring police into danger

Police block off part of the Broadway tourist district on Monday after the Christmas Day bombing in Nashville. (Mark Humphrey/AP)

Early on Christmas morning, a man drove a recreational vehicle into downtown Nashville and detonated a giant explosive, killing himself and destroying portions of the town center. After parking the RV but before detonating the device, the man whom investigators have identified as Anthony Q. Warner set off an exterior sound system that blared a repetitive audio message to residents, shop owners and passersby. An automated voice warned: “This area must be evacuated now. If you can hear this message, evacuate now.” The audio loop was followed by a 15-minute countdown to the blast, which injured three people including a police officer. Warner was the only fatality.

Why would an attacker alert Nashville residents and police before setting off an explosive device? If the goal of bombings is to kill and maim, why give up the advantage of surprise? Many terrorists, both lone actors and larger groups, have offered “fair warning” to potential victims. My research on terrorist threats shows that warnings make political sense: Terrorists trying to persuade civilians and garner local support for their cause cannot afford to look mindlessly bloody. They give warnings to allow civilians a way out, making themselves look more reasonable and legitimate in the public eye.

Was it terrorism?

Although the police investigation is ongoing, the Nashville bombing certainly looks like terrorism — defined in scholarship as politically motivated violence and threats to coerce or alter the perceptions of a broader audience. The attacker detonated a bomb that damaged buildings and destroyed AT&T’s local telephone infrastructure, disrupting phone service, the 911 system and service at Nashville’s airport. Police are reportedly investigating whether the bomber was driven by online conspiracy theories to attack 5G cellular phone companies falsely blamed for the coronavirus pandemic. Warner also died in the attack, making it look like a suicide bombing. (We don’t know yet whether Warner intended to kill himself, as in a true suicide attack, or whether his death was accidental.)

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Why do terrorists give warnings?

Terrorists are not always trying to hurt or kill the largest number of people. Terrorist groups, particularly domestic organizations that hide among a civilian population, often limit their impact on civilians by alerting them before attacks. That was common among 1970s “New Left” groups like the Weather Underground or loosely affiliated individuals such as Sam “Mad Bomber” Melville, who mounted a destructive but nonlethal 1969 dynamite campaign against government buildings and other targets associated with the Vietnam War. Warnings were also commonly offered by organizations like the Irish Republican Army, the Basque separatist group ETA, and to a lesser extent the West African extremist group Boko Haram. We sometimes see these tactics in suicide attacks, when the attacker seeks to get as close as possible to a target but does not wish to kill civilians.

Terrorists who want civilian support, rallying them to a cause or soliciting their material help, must tend their image with those civilians, working to appear as the representatives of a legitimate cause. That concern is particularly acute when fighting democracies that set relatively high standards for respecting human rights. Thus, terrorists face what I call a “multiple audiences conundrum,” as they simultaneously want to intimidate and coerce enemies without alienating potential supporters locally. Warnings help: Terrorists can level buildings and infrastructure, projecting strength to their foes, while sparing most civilians and projecting an image of relative restraint. The qualifier “relative” is important, because even with warnings, bombs may kill or maim noncombatants.

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But there’s a darker reason for warnings

Warnings tend to draw police and other first responders into danger. Nashville police initially arrived after reports of gunfire and were greeted with an incongruous audio recording of Petula Clark’s hit song “Downtown.” These confusing signals led some law enforcement to wonder whether police were the targets, having been drawn downtown and then given just 15 minutes to evacuate residents and themselves.

That possibility reveals how complex terrorist threats can be. As my research shows, the same warning that spares civilian life can put security forces at deadly risk. Police in Northern Ireland face such dangers still, with militant Irish Republican groups using warnings and deceptive hoax threats to bait police, whom Irish Republican radicals see as military targets, into shootings and explosions.

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Truthful warnings can also increase the potential for disruptive malfeasance. Once civilians and law enforcement know that threats may well be accurate, terrorists and unscrupulous individuals can issue hoax threats that disrupt business, snarl public transit and shutter educational institutions. That’s common at Nigerian schools, which face false threats from Boko Haram and disgruntled students alike. They are also common at U.S. schools: A 2015 hoax threat, purportedly from Islamist militants, shut down all 900 Los Angeles public schools for a day, affecting hundreds of thousands of students and parents.

Attacks of this kind often spark copycat attempts. The Nashville attack may already be inspiring hoaxes: Two days later, a Tennessee sheriff’s office arrested a driver for parking a box truck outside a convenience store, blaring audio “similar to what was heard” before the Christmas attack.

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Joseph M. Brown (@Joseph_M_Brown) is an assistant professor of political science at the University of Massachusetts Boston and author of “Force of Words: The Logic of Terrorist Threats” (Columbia University Press, 2020).