On the morning of February 26, 1993, Islamic militants steered a nondescript Ryder van through the winding darkness of the parking garage under the World Trade Center. They had spent years planning this moment in secret meetings at mosques and jailhouses, in rural outposts that served as paramilitary camps, and in safehouses where explosive compounds were mixed in makeshift labs.

Loaded into the van's rear compartment was a 1,400-pound chemical bomb...

...It had been the intention of the World Trade Center bombers to annihilate tens of thousands of Americans, in addition to rendering the world's most significant financial district uninhabitable. Detonation was consciously timed for maximum carnage: high noon on a Friday, when as many as 120,000 business professionals, laborers, diners, tourists, and area residents typically swarmed the Twin Towers and their immediate Wall Street environs.

More diabolically [Note: He did not say innovatively], not content with their sophisticated, powerfully combustible urea-nitrate mixture, the jihadists laced the compound with deadly sodium cyanide and attempted to boost the explosion with hydrogen tanks. The aim was a horror virtually unimaginable back then (though it is, today, an omnipresent fear): wide dispersal of a lethal, aerated chemical, killing the thousands too distant to be obliterated by the sheer force of the blast...

... That they would learn from their errors faster than we from ours is now clear. In truth, it was clear then. On the hard drive of Nidal Ayyad, one of the bombers arrested in early March 1993, the FBI recovered a claim-of-responsibility letter. It is even more chilling today than it was all those years ago:

We are, the Liberation Army fifth battalion, again. Unfortunately, our calculations were not very accurate this time. However, we promise you that next time it will be very precise and World Trade Center will continue to be one [of] our targets unless our demands have been met.

And so it was.