Seems obvious to me:

“I reject the notion that Al Qaeda is waiting for ‘the big one’ or holding back an attack,” Sheehan writes. “A terrorist cell capable of attacking doesn’t sit and wait for some more opportune moment. It’s not their style, nor is it in the best interest of their operational security. Delaying an attack gives law enforcement more time to detect a plot or penetrate the organization.”

Terrorism is not about standing armies, mass movements, riots in the streets or even palace coups. It’s about tiny groups that want to make a big bang. So you keep tracking cells and potential cells, and when you find them you destroy them. After Spanish police cornered leading members of the group that attacked trains in Madrid in 2004, they blew themselves up. The threat in Spain declined dramatically.

Indonesia is another case Sheehan and I talked about. Several high-profile associates of bin Laden were nailed there in the two years after 9/11, then sent off to secret CIA prisons for interrogation. The suspects are now at Guantánamo. But suicide bombings continued until police using forensic evidence—pieces of car bombs and pieces of the suicide bombers—tracked down Dr. Azahari bin Husin, “the Demolition Man,” and the little group around him. In a November 2005 shootout the cops killed Dr. Azahari and crushed his cell. After that such attacks in Indonesia stopped.

The drive to obliterate the remaining hives of Al Qaeda training activity along the Afghanistan-Pakistan frontier and those that developed in some corners of Iraq after the U.S. invasion in 2003 needs to continue, says Sheehan. It’s especially important to keep wanna-be jihadists in the West from joining with more experienced fighters who can give them hands-on weapons and explosives training. When left to their own devices, as it were, most homegrown terrorists can’t cut it. For example, on July 7, 2005, four bombers blew themselves up on public transport in London, killing 56 people. Two of those bombers had trained in Pakistan. Another cell tried to do the same thing two weeks later, but its members had less foreign training, or none. All the bombs were duds.

[…]

Sir David Omand, who used to head Britain’s version of the National Security Agency and oversaw its entire intelligence establishment from the Cabinet Office earlier this decade, described terrorism as “one corner” of the global security threat posed by weapons proliferation and political instability. That in turn is only one of three major dangers facing the world over the next few years. The others are the deteriorating environment and a meltdown of the global economy. Putting terrorism in perspective, said Sir David, “leads naturally to a risk management approach, which is very different from what we’ve heard from Washington these last few years, which is to ‘eliminate the threat’.”

Yet when I asked the panelists at the forum if Al Qaeda has been overrated, suggesting as Sheehan does that most of its recruits are bunglers, all shook their heads. Nobody wants to say such a thing on the record, in case there’s another attack tomorrow and their remarks get quoted back to them.

That’s part of what makes Sheehan so refreshing. He knows there’s a big risk that he’ll be misinterpreted; he’ll be called soft on terror by ass-covering bureaucrats, breathless reporters and fear-peddling politicians. And yet he charges ahead. He expects another attack sometime, somewhere. He hopes it won’t be made to seem more apocalyptic than it is. “Don’t overhype it, because that’s what Al Qaeda wants you to do. Terrorism is about psychology.” In the meantime, said Sheehan, finishing his fruit juice, “the relentless 24/7 job for people like me is to find and crush those guys.”