Know thy enemy is an ancient principle of warfare. And if America had heeded it, it might have refrained from a full-scale "war" on terrorism whose price tag is touching $2 trillion. That's because the Islamist enemy it is confronting is not some hyper-power capable of inflicting existential—or even grave—harm. It is, rather, a rag-tag band of peasants whose malevolent ambitions are far beyond the capacity of their shallow talent pool to deliver.

The shock and awe of 9-11 was so great that Americans came to think of Islamist jihadists as a low-tech version of Dr. Strangelove, an evil genius constantly looking for ingenious ways of spreading death and destruction. America is so open and vulnerable and the Islamists so crafty and motivated that it was just a matter of time, everyone thought, before they got us again.

But this year marks the 10th anniversary of 9-11 and none of the horrible scenarios conjured then have materialized. Islamic terrorists have not flown more planes into buildings. They haven't detonated "loose nukes" or dirty bombs. They haven't released nerve gas into subway stations. They haven't poisoned the water supply. They haven't even strolled into one of America's hundreds of malls or farmer's markets and blown themselves up.

Maybe this is because enhanced post-9/11 security has made America invulnerable. Or maybe the Islamists never posed that a big threat to begin with.

Most intelligence experts interviewed by The Washington Post for a series on nuclear, biological, and chemical attacks (the easiest of the three) three years after 9/11 agreed that anything requiring scientific expertise is virtually impossible to pull off for Al Qaeda—the only group in the so-called global jihadist movement with any ambition to strike on American soil. If anything, Al Qaeda's capacity has shrunk not grown since then. But even campaigns of conventional, low-tech terrorism that the Palestinian intifada unleashed in Israel or the Islamist insurgency has fomented in Kashmir is difficult to export across borders. They can't be planned from overseas. They need people on the ground. And Al Qaeda has two ways to put them there. It can either recruit from within America or smuggle them in, as it did with the 9-11 hijackers.

The problem with the first option is that open societies are not good breeding grounds for radicals willing to die for the sake of 72 virgins in the other world. It is no coincidence that a decade-long FBI search has failed to find a single genuine Al Qaeda cell in the United States. Forget the U.S. where the local Muslim population is fairly assimilated: Glenn Carle, an operations officer or spy with the CIA for 23 years, notes that Al Qaeda has failed to do meaningful recruitment even in Europe, where Muslims are much more disaffected, attracting no more than a few hundred to training camps in Afghanistan over the years.

As for smuggling people in, that wouldn't be a problem for Al Qaeda—no matter how many fences we build or how many visas we deny. Its main obstacle is finding individuals worth smuggling in given the skill set needed for the job. They would have to be: radicalized enough to die for their cause; Westernized enough to move around without raising red flags; ingenious enough to exploit loopholes in the security apparatus; meticulous enough to attend to the myriad logistical details that could torpedo the operation; self-sufficient enough to make all the preparations without enlisting outsiders who might give them away; disciplined enough to maintain complete secrecy, and—above all—psychologically tough enough to keep functioning at a high level without cracking in the face of their own impending death.

That emphatically is not the profile of an average Al Qaeda foot solider who is a semi-literate peasant with barely any experience of the world outside his province. According to Carle, at its height, Al Qaeda had maybe a couple of dozen individuals who could be regarded as officer material. Out of them, only a very small subset would even come close to fitting the bill for a trans-national terrorist. One big disadvantage inherent in the terrorist enterprise of course is that it expends its best people in every successful attack, something that is not conducive to building a deep bench of terrorist talent overtime.

It is hardly any surprise then that Al Qaeda can scrape together a team to stage something spectacular only every decade or so. There has been talk lately about it turning to a new strategy of small attacks or microterrorism such as the bomb packages from Yemen. But such attacks are probably not worth its while given that the international backlash they would generate would be far more enduring than the fear they engender in America. In any case, this is hardly the kind of thing that would justify a "war."

An attack that kills 3,000 citizens—even if only once every 10 years—is nothing to ignore of course, and some limited effort to clean out Al Qaeda in Afghanistan might have been justified. But is it worth spending $1 trillion on two ongoing wars and $1 trillion on enhanced homeland security—America's post-9-11 terrorism expenditure? America spends more on intelligence than the rest of the world put together.

John Mueller, a political science professor at Ohio State University, points out that chances of an American being killed by international terrorism during his or her lifetime is about one in 80,000. More people drown in bathtubs every year. "Even if there were a 9/11 scale attack every three months for the next five years, the likelihood that an individual American would be among the dead would be two hundredths of a percent or one in 5,000," he notes.

Security hawks—just like climate change warriors—maintain that no expenditure is too big to deter another attack. But that is utter foolishness. A country sacrifices lives when it ignores bigger threats to fight smaller ones.

Over 5,000 American soldiers have died in Afghanistan and Iraq without on balance saving any civilian lives. It is time to call off the "war" on terrorism. Al Qaeda is not worth it.

Shikha Dalmia is a senior analyst at Reason Foundation and a columnist at The Daily, America's first iPad newspaper. A version of this article originally appeared at The Daily.

