On September 11, 2001, specifically the moment passengers on UA93 learned that three other hijacked liners had been crashed into the World Trade Center and the Pentagon, the U.S. forever ceased to be vulnerable to such hijackings. Never again would passengers follow the FAA’s regulation not to interfere with hijackers. Not ISIS or anyone else can change that.

Nor is an event similar in sophistication to 9/11’s to be expected from ISIS. What we know (and especially what we do not know) about 9/11 bespeaks the expertise and connections of a national intelligence service. Consider: while the names on the airplane manifests match the photos of visa recipients, they do not match the hijackers who actually boarded the flights. Sophisticated identity thefts. While Mohammed Atta ostentatiously wired his leftover funds to an unprotected al-Qaeda account, the funds had come to him from accounts so scrubbed that they still hide their provenance. As Czech President Vaclav Havel confirms, Atta met twice with Iraqi intelligence officer al-Ani in Prague. In the U.S., the hijackers got help from Saudi diplomats and from Saudi-financed mosques. During the hijacking, they turned off transponders—which they could not have learned at the U.S. flight schools they had attended desultorily. None of this is a hallmark of Afghan mountain caves. No such things are likely to originate in Raqqa or Mosul.

But no sophistication is needed to wreak havoc on America comparable to that of 9/11. Nothing could stop untrained men from closing down the entire U.S. school system by throwing flaming gasoline bottles onto school buses in many cities at precisely the same time. Consistently, “red team” tests show that the Kabuki theater that is our airport security system cannot stop suicide bombers from bringing explosives onto U.S. passenger planes. The training for this is less than what “drug mules” get for transporting “stuff” in their body cavities. The same goes for rolling explosives-laden luggage into airport security lines or firing RPGs into tankers in U.S. ports. All such things are well within ISIS’s tactical capability.

ISIS, however, is attacking America in a manner yet simpler and potentially far more devastating: It is doing its best to inspire some Americans to nurse their perceived grievances and to act upon those grievances under the rubric of revolutionary Islam, with the intent to cause Americans to look on one another as potential murderers and targets for murder. Increasing all Americans’ fears, suspicions, and antagonism—especially of the tribal kind—has an effect disproportionate to the number of those killed. Over two generations, radical Islamists have had some success in inducing thousands of Americans to sympathize and even to identify with radical Islam as some sort of an alternative to American loyalty. ISIS is capitalizing on that avenue to convince the estranged to step from disaffection to violence.

9/11, for all its horror, was something done to America by foreigners. As such, it united Americans. ISIS is stoking war among Americans.

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