Last night, Manchester Arena issued a statement that “the incident took place outside the venue in a public space.” This morning authorities say the bomb detonated near the box office in the foyer of the arena.

After a horrific attack in a public place like this, there’s always an instinct to add more layers of security to public events – metal detectors, vehicle check points, jersey barriers, and so on. Unfortunately, this approach really doesn’t work, as it just moves the terrorist’s best location to strike further outward.


Yes, jersey barriers can keep car bombs from buildings, metal detectors can keep out guns, and dogs can sniff out bomb chemicals. But all a suicide bomber (or aspiring mass shooter, or one perpetrator of any kind of attack) needs is a crowd. Metal detectors create lines, choke points, and people gather closer and closer together… which is what the suicide bomber wants. There are just too many ways for a crowd to form in our society – commuters, popular restaurants, busy intersections… by the time the suicide bomber has his device assembled, it’s almost too late. Our counterterrorism efforts have to focus on stopping them before they have their devices ready to go – which requires undercover work, electronic and Internet surveillance, paid informants, and the close cooperation of intelligence agencies and law enforcement.

One of the more interesting debates in counterterrorism circles in the past decade has been whether the long and arduous security clearance process makes it harder to recruit immigrants, who speak the language, know the culture, will more easily infiltrate a cell or pick out a dangerous radical. The New York Police Department doesn’t have to follow federal standards for a security clearance, and boasts that because of this, they have a much better network of informants:

“With local law enforcement,” New York Police Commissioner Ray Kelly told me in 2008, “you have more flexibility in recruiting confidential informants, and obviously in arresting people. The whole package is in one agency.” The operative word is “flexibility.” And when that “agency,” the NYPD, has more than 35,000 sworn officers of the law in a city of 8.5 million people, 40 percent of whom were not born in the United States, there’s a lot of potential to gather information. If hundreds of your cops come from immigrant backgrounds themselves and speak languages like Arabic, Urdu, and Farsi with native fluency, that helps, too.


Then again, this may be just a matter of manpower. The counter-terrorism forces in the United Kingdom are very, very good and painfully experienced, not just from the likes of al-Qaeda but from the bad old days of the IRA before that. But if your country has hundreds of potential terrorists…