After al Qaeda set out in 1999 to deliver a devastating attack on America using hijacked airplanes, only one thing worked right in the nation's defense.

According to the final report of the 9/11 commission, it wasn't the FBI, CIA, FAA or Air Force. Not the National Security Council or the Department of Defense. Not the State Department or Border Patrol. Not Congress or any president.

"The institutions charged with protecting our borders, civil aviation, and national security did not understand how grave this threat could be, and did not adjust their policies, plans, and practices to deter or defeat it," the bipartisan commission unanimously declared.

Only a small band of civilians, strangers to one another -- without benefit of staff meetings, bylaws, uniforms or task forces -- communicating by cell phone with loved ones who happened to be watching TV -- managed to figure out what was going on in time to thwart a guided-missile attack on Washington.

Brave passengers aboard United Airlines Flight 93 forced hijackers to crash the plane into an empty field far short of its target.

The final report is a document of historic breadth and almost unprecedented detail, offering the sort of examination of a highly classified subject that customarily would not be possible for decades after the fact. From the findings of spy agencies to the tactics of fighter pilots, from the conversations of heads of state to the verbatim texts of secret presidential briefings, this is the government laid bare.

It is not a pretty picture.

Many of the specifics have been revealed in interim reports released by the commission in recent months. Here, they come together in a long and depressing narrative, by far the most comprehensive account of the catastrophe available.

It begins with a view of the enemy larger than just Osama bin Laden and his al Qaeda operation. "The problem is that al Qaeda represents an ideological movement, not a finite group of people. It initiates and inspires, even if it no longer directs," the commissioners found. "Killing or capturing [bin Laden], while extremely important, would not end terror."

Unforeseen -- yet lethal -- this new challenge to American security rose quickly from the ruins of the Cold War. U.S. agencies, configured to fight the Soviets, were caught flat-footed.

Even after bin Laden called on Muslims everywhere to kill Americans wherever they found them -- and then pulled off coordinated attacks on U.S. embassies in Kenya and Tanzania -- the U.S. response was feckless, because of bureaucratic squabbling, poor communications, misdirected resources and "failures of imagination."

The signs were there. Radical Islamists associated with 9/11 plotter Khalid Sheik Mohammed hit the World Trade Center with a truck bomb in 1993, and two years later were discovered plotting mass hijackings of U.S. airliners. Nevertheless, bin Laden and Mohammed had no trouble, between 1999 and 2001, communicating, meeting and planning the destruction of the twin towers using hijacked planes. Indeed, the summer of 2001 was "a drumbeat" of alarming, if unspecific, reports that -- as President Bush was told in August of that year -- "Bin Laden Determined to Strike in U.S."

"The 9/11 attacks were a shock," the panel concluded, "but they should not have come as a surprise."

CIA Director George J. Tenet wanted to declare war on al Qaeda in 1999, but he had no covert agents to fight it. The Pentagon had all the resources to fight a war, but no obvious desire: "At no point before [the attacks] was the Department of Defense fully engaged in the mission of countering al Qaeda." Diplomacy was tried, but President Clinton and his State Department failed to persuade Pakistan to use its influence to push bin Laden out of Afghanistan. All the while, Congress showed scant interest in determining whether yesterday's national security mechanisms were ready for tomorrow's problems.

"Blame, if there's blame, has to be spread all across the board," commissioner James R. Thompson (R), a former governor of Illinois, said yesterday. Even the public could be said to have failed, "because the American people never demanded more or better."

Even the government's successes quickly turned to failure: Various FBI agents came across important clues to the unfolding plot but could not get that information through the walls separating agencies. The CIA tracked some of the terrorists but failed to keep them out of the country. Once they were in the country, no one added their names to the no-fly list.

Even on the morning of the attacks, several hijackers were identified by an airport screening program for special review. But the review was designed to keep bombs out of baggage, while the bombs were those winged tubes parked at the gates.

The enemy had evolved. U.S defenses had not.

Time will no doubt surface a few more intriguing papers, and perhaps an important witness or two will yet be located -- perhaps in a mountain cave on the Afghanistan-Pakistan border.

Yet, the 9/11 commission report had the meaty feeling of a history that will endure, thanks to the political pressure, and the subpoena power, that opened up more than 2.5 million pages of information and the testimony of 1,200 interviews. Though quick, the historical judgment seems conclusive: That American leadership failed across the board.

The panel's recommendations also felt historic. Arguing that 9/11 was but an early battle in a global struggle, the commissioners proposed major changes at the Pentagon, the CIA, the FBI, the State Department, the White House, Congress, the private sector -- and more.

Not since the outbreak of the Cold War more than 50 years ago has such an enormous rethinking of American government been seriously contemplated. No sooner was the document released than Commissioner Bob Kerrey (D), a former senator from Nebraska, pronounced himself "not optimistic" that so many entrenched interests and hidebound bureaucracies could be compelled to surrender prerogatives and recalibrate power.

"This is the challenge of our generation," said the commission chairman, Thomas H. Kean (R), a former governor of New Jersey, and it demands not just exhortations and appropriations -- those Washington stocks in trade -- but a whole new way of doing business.

And fast.

Loreen Sellitto, left, who lost a son, Matthew, in the 2001 attacks, and Elaine Hughes, who lost a son, Kris, attend a news conference about the Sept. 11 commission's findings.Customers wait at the Government Printing Office store to purchase copies of the 567-page final report of the 9/11 commission.