Of course, 20-20 hindsight over the Sept. 11 terrorist attack is a lot easier than predicting an approaching national disaster. Of course, targeting a few culprits and squabbling over which president was to blame won’t help matters. Even so, the U.S. government and the American people must find out how the deadly attacks on New York and Washington might have been prevented and how to anticipate and possibly head off future terrorist attacks.

That’s why the long-awaited 850-page report released last week by the Congressional Joint Committee on Intelligence is so important. And that’s why an expanded investigation by a bipartisan commission appointed by Congress and President Bush, with its report due next May, should be even more significant.

In a devastating terror chronology, the joint committee report lists the first World Trade Center bombing in 1993, the plot in the same year to bomb other New York City landmarks, the 1998 bombing of two U.S. embassies in Africa, and the October 2000 bombing of the USS Cole in Yemen – all of them traceable to Osama bin Laden’s radical Islamic conspiracy.

A parallel chronology lists bin Laden’s public declaration of war against the United States in May 1998 and a string of intelligence intercepts of terrorist plans to attack a government facility in Washington in the spring of 1999, to assassinate the U.S. secretaries of state and defense and the director of central intelligence in August 1999, to attack landmarks in California and New York City in September 1999, to attack targets in Washington and New York during the millennium celebrations at the beginning of 2000, to bomb the Statue of Liberty and other landmarks including skyscrapers in March 2000, and in April 2001 to use commercial pilots in “spectacular and traumatic” attacks like the first World Trade Center bombing.

An intelligence report in December 1998 said: “Plans to hijack U.S. aircraft proceeding well. Two individuals had successfully evaded checkpoints in dry run at NY airport.” The director of central intelligence, George Tenet, did declare in December 1998 in a memo to CIA senior managers that “we are at war” against bin Laden and “I want no resources or people spared in this effort either inside CIA or the community.” Yet the word did not reach most other senior government officials.

“In short,” the report concluded, “the D.C.I. (director of central intelligence) and other intelligence community officials recognized the bin Laden threat. Notwithstanding the D.C.I.’s declaration, President Clinton’s August 1998 statements, and intelligence reports to policymakers over many years indicating that bin Laden was waging war on the United States, neither President Clinton nor President Bush nor their National Security Councils put the government or the intelligence community on a war footing before September 11.”

Among the joint committee’s recommendations are better and faster sharing of intelligence among government agencies, development of a national watch list center, reduction of government secrecy when used as “a shield to protect agency self-interest,” and “vigorous and continuing oversight of the community’s work in this critically important area.”

More such information and additional recommendations will soon be coming from the congressional-presidential commission. Its chairman, Thomas H. Kean, a former Republican governor of New Jersey, and vice chairman, Lee H. Hamilton, a former Democratic House member from Indiana, said they hope their report will be made fully public and free of the heavy editing that the CIA imposed on the congressional report. Much of the blacked-out material in that report concerned members of the Saudi Arabian government and royal family, including extensive connections between several of the hijackers with Saudi men living in the United States on Saudi pay.

Such information must be made public. The American people deserve no less.