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After ISIL, how likely is another 9/11?

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Four years ago last week, an al Qaeda splinter group calling itself the Islamic State in Iraq and the Levant declared the formation of a global caliphate. Throughout 2014, ISIL acquired a broad swath of territory across Iraq and Syria — a safe haven in which it could train militants, plot attacks and compile resources. Using guns, explosives and trucks, ISIL-affiliated terrorists carried out attacks from Istanbul, Turkey, to Orlando, Florida, heightening fears of another 9/11-scale terrorism event. After a four-year, U.S.-led campaign wiped out its safe haven, ISIL is a shell, its remnants in hiding or on the run. Nonetheless, according to a recent Axios poll, Americans still view ISIL as a bigger threat than a nuclear-armed North Korea or a rapidly-rising China.

Many Americans wonder: Why has there been no mega-terrorist attack on the United States since Sept. 11, 2001? In the wake of that attack, which killed 3,000, anyone who had offered to bet that 17 years on there would be no terrorist attack on the United States that killed more than 100 people could have gotten 1,000:1 odds.

{mosads}Have we just been lucky? As Tom Friedman has put it, noting a series of close calls such as the Times Square bomb plot in 2010, have we “won the lottery five times in a row”? Have U.S. government actions in response to 9/11 shifted the odds? Or, recognizing the contribution of hard work and good fortune, should we acknowledge that there remains a larger mystery we still don’t understand? The unsatisfying but correct answer is: all of the above.


Every year since the 9/11 attack, the annual threat assessment issued by the U.S. Intelligence Community has never ranked terrorism lower than the top three threats to the United States. In its Preventive Priorities Survey of foreign policy experts, the Council on Foreign Relations consistently labels terrorism a “top-tier risk” to the United States, based on likelihood and impact. Today, half of Americans expect that they or a member of their family will be killed by terrorists.

If we contrast these reports with a review of who or what has actually killed Americans here in the United States since 9/11, the gap is striking. If the future resembles the past, those who fear for their lives should not look behind them for a terrorist, but rather look up. Tree limbs and other falling objects have killed 100 times more Americans than terrorists in each of the past 17 years. In a single city in Massachusetts that has just 21,000 citizens, tree limbs killed two in a single week in 2016. Apart from old age and disease, the leading causes of death for Americans here at home have been opioid overdoses (40,000); car accidents (39,000); and suicide (38,000). Among 17 ranked killers, terrorism is last.

It is hard to deny the gap between the predictions of our policy community and intelligence analysts, on the one hand, and the brute facts, on the other.

How can we explain this gap between expectations and experience? Unquestionably, many of the actions taken since 9/11 have prevented attacks. Osama bin Laden had active plans for additional attacks, including aspirations for a nuclear 9/11. What prevented that, first and foremost, was a relentless counterterrorism campaign that killed or captured most of al Qaeda’s leadership and left the others spending most of their time trying to survive rather than perfecting plots for future terrorist attacks. Destruction of their headquarters and training camps meant that thousands of individuals who would have been planning, training and then conducting terrorist attacks never got their chance.

At the same time, examining this challenge through Sherlock Holmes’ “MMO” framework — motive, means and opportunity — we find that terrorists continue to have more than enough of all three. Potential perpetrators motivated to conduct terrorist attacks on the United States have multiplied beyond anyone’s expectation in 2001. By invading Iraq and Afghanistan, and conducting drone strikes and special forces raids in seven Muslim-majority countries — killing individuals we labeled “terrorists” but also civilians — the United States has provided fodder that al Qaeda splinter-groups such as ISIL have used skillfully to recruit and motivate payback.

The means to kill hundreds, and even thousands, of Americans abound. As the Orlando and Las Vegas shootings demonstrated, it is not that hard to acquire or modify a specialized rifle that will allow a shooter to fire 1,000 rounds in two minutes. The internet makes available recipes for homemade bombs, chemicals and even biological pathogens. As military planners would put it, the United States offers a “target-rich” environment. Terrorists intent on killing large numbers could find opportunities everywhere, from malls and movie theaters to sports stadiums and churches.

Therefore, what? We should recognize that in the shock of 9/11 we may have overestimated the likelihood of another mega-terrorist attack, and thus may not understand the fundamentals of this challenge as well as we thought. But I worry that our good fortune in experiencing 17 years without a successor to the 9/11 attack will encourage complacency. Given the immense challenge posed by a rising China, a resurgent Russia, and a nuclear North Korea, I endorse the Trump administration’s decision to push terrorism further down on the spectrum of threats. And I applaud the success of the counter-ISIL campaign that defeated the “caliphate” in Iraq and Syria. But we should never forget that most of the planning and preparation for the 9/11 attack was done by an al Qaeda cell in Hamburg, Germany.

We must sustain our efforts to deny terrorists both the means (especially nuclear and biological) and opportunities to achieve their deadliest ambitions. When we compare the cost of these efforts with the consequences if we failed, the case for preventive action remains compelling.

Graham Allison is a leading analyst of U.S. national security and defense policy with a special interest in nuclear weapons, terrorism and decision-making. Founding dean of the modern Kennedy School at Harvard, he was director of the Belfer Center for Science and International Affairs from 1995 until July 2017. He served as assistant secretary of defense in the first Clinton administration, and was a special adviser to the secretary of defense under President Reagan. 

Tags 9/11 terrorist attack Islamic State of Iraq and the Levant terrorism threat

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