Deterring ISIS.

• Author: Allison, Graham T.
• Position: The Realist

In the wake of the Orlando and Istanbul attacks, President Obama reiterated his determination to "destroy" ISIS by executing a strategy that combines air strikes, American special-operations units and support for local ground forces. Both of the candidates campaigning to succeed him insist that the United States must do more: Donald Trump advocates that Washington "bomb the hell out of" the group, while Hillary Clinton promises to "smash the would-be caliphate." All three, however, are in violent agreement on one point: the overriding objective must be to destroy ISIS.

The insistence on the "destruction" of ISIS has become such a reflexive linchpin of Americas counterterrorism project that few pause to consider its strategic merit. But the nation with arguably the most experience and success combatting terrorism has considered it--and found it wanting.

Israelis live much closer to ISIS than do Americans. ISIS has pledged to conquer the Jewish state and incorporate it into its core caliphate. Yet surprisingly, the Israel Defense Forces (IDF) has rejected the option of taking the fight directly to ISIS. Instead, faced with an operational threat that could mean the death of hundreds of Israelis at any moment, it has embraced a strategy that has not even been on the U.S. policy menu. Adopting a page from the playbook the United States used to defeat revolutionary Soviet-led communism in the Cold War, Israel is preventing ISIS attacks through a strategy of patient, vigilant deterrence. Obviously, the United States cannot simply adopt the Israeli approach whole cloth. It operates in a different security environment than the Jewish state, which faces a multiplicity of terrorist threats on its borders. But there are important lessons that America can learn to enhance its national security.

Israel's approach to ISIS is straightforward. Israel seeks to persuade ISIS not to attack it by credibly threatening to retaliate. If you attack us, the thinking goes, we will respond in ways that will impose pain that exceeds any gain you can hope to achieve. As Cold War strategists learned, making this work in practice is demanding. To be effective, deterrence requires three Cs: clarity, capability and credibility. Specifically, this means clarity about the red line that cannot be crossed, communicated in language the adversary understands; capability to impose costs that greatly exceed the benefits; and credibility about the willingness to do so. Failures occur when the deterrer falls short on any one of the three Cs. So, if I draw a red line, you cross it, and I respond with words rather than the decisive punishment threatened, I fail the third C. Whatever excuse I give for not executing my threat, and however earnest my claim that next time will be different, the blunt fact is that adversaries will find my threats less credible.

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If that were not enough, as the great nuclear strategist Thomas Schelling taught us, successful deterrence requires more than just a threat. The flip side of the deterrence coin is an equivalent promise: if you refrain from the prohibited action, I will withhold the threatened punishment. If, for whatever reason, I decide to administer the specified punishment even though you have complied with my demands, I spend that coin--and can no longer use that threat to deter you. As the saying goes, if you're damned if you do and damned if you don't--you might as well do.

The suggestion that terrorists as vicious as ISIS could be deterred is routinely dismissed by most members of the U.S. policy community as silly or dangerously naive...