This is the second of five chapters of an investigation supported generously by the Fund for Investigative Journalism and the George Polk grants for investigative reporting administered by Long Island University.

As amazing as it seems now, there was resistance to investigating Sept. 11. Twenty-two House Republicans voted against authorizing a study by the National Institute of Standards and Technology (NIST). President George W. Bush resisted the creation of the National Commission on Terrorist Attacks Upon the United States, a.k.a. the 9/11 commission. Mayor Michael Bloomberg took no questions from the 9/11 commission when it came to New York to investigate the city's response, and for a time he blocked the release of official records to the NIST investigators and the 9/11 commission, because the city was fighting an ultimately successful New York Times lawsuit to make the records public.

Meanwhile, neither the FDNY's Safety Battalion nor the National Institute for Occupational Safety and Health (NIOSH), which routinely probe firefighter deaths, investigated the World Trade Center fatalities. "At the time, I just think because of the magnitude of the event, nothing was done," says Tim Merinar, who leads NIOSH's firefighter fatality investigations. "I don't really think any organization did a true fatality investigation of the incident." (In fairness, the scale of the losses would have made such investigations, which detail the precise circumstances of each death, difficult to complete.)

Despite these obstacles, three reports—the NIST study, the 9/11 commission investigation and an FDNY-authorized report by the consultant McKinsey & Co.—managed to, very delicately, spell out Sept. 11's painful lessons for the city and its fire department.

Death in a disaster usually has multiple causes. You could talk about the Titanic and focus on the iceberg, not the lifeboats. You could discuss Hurricane Katrina and omit any mention of the levees. You could blame the Hindenburg only on static electricity. But none of these would give a full accounting of why people ended up injured or dead.

Sept. 11 would never have happened if terrorists hadn't decided to kill Americans. But it might have taken a lower toll on the fire department if problems with communications and personnel had been averted.

What was the mission?

Fighting fires in high-rise buildings is very different from battling blazes in shorter structures. Firefighters can't leave a tool in their truck and run down to get it or easily step outside for a new tank of air. Most important, they usually have to use a water system built into the high-rise building to put out the blaze. Even when that water is available, some high-rise fires are simply too large to put out. To extinguish even a flaming half-floor of the WTC would have required, by NIST's calculations, 1,250 gallons of water a minute, a deluge that might take 10 engine companies to provide.

Rescuing people in high-rise buildings is complicated too. The time it takes a person wearing at least 50 pounds of gear to climb dozens of flights of stairs could be longer than the time a civilian can survive trapped amid toxic smoke.

All these challenges were exacerbated on Sept. 11. Not only were multiple, huge floor areas in flame, the fires were also whipped by wind pouring in through the buildings' shattered sides. The standpipes in both buildings were believed to have been severed by the aircrafts' impact, meaning no water could reach the upper floors. The elevators were—with a single exception in each tower—rendered immobile, robbing firefighters of a method for reaching the fire faster.