The war over Iraq — not to be confused with the conflict actually taking place there — is back in the headlines. This week's report to Congress by America's top two emissaries in Baghdad, Gen. David Petraeus and Ambassador Ryan Crocker, will provide a backdrop for the momentous decisions to come concerning whether and how to pursue victory in Iraq.

Before the politicians and their constituents make such decisions about where we go from here, they should be sure to ground themselves in the facts about how we got to this point. After all, as George Santayana put it, "Those who cannot learn from history are doomed to repeat it."

Fortunately, it has just become considerably easier to understand the history of the decision to make Iraq a central front in the larger War for the Free World and to dissect what was and was not done right — and how to achieve better results in the future. Today marks the publication of an extraordinary new book on the subject, "War and Decision: Inside the Pentagon at the Dawn of the War on Terror," by former Defense Undersecretary Douglas Feith.

Now, Doug Feith has been a valued friend and colleague of mine for 25 years. Consequently, I know him to be scrupulous in his command of the facts, exacting in his analysis and lucidly articulate in his writing.

Still, I was unprepared for the thoroughness of the documentation, the sweeping nature of the narrative and the highly readable prose with which "War and Decision" depicts the actions precipitated at the highest levels of the U.S. government by the Sept. 11, 2001, attacks.

Particularly edifying are Mr. Feith's exploration of the serious policy differences between various decisionmakers and the material contribution of those disagreements to the preparation, execution and aftermath of overthrowing Saddam Hussein's regime.

In contrast to previous books and memoirs on the subject published to date, Mr. Feith's is not aimed at self-promotion or self-vindication. Neither is it an effort to settle scores with those who have, in some cases viciously, attacked the author in their own screeds.

Rather, it is the first attempt by a serious student of history to lay out the myriad, challenging choices confronting a president who, within eight months of taking office, witnessed a devastating attack on this country and resolved to prevent another — possibly far more destructive one. The considerations, competing recommendations and presidential and Cabinet-level decisions that shaped the Bush administration approach to the terrorist threat from state-sponsored networks are documented in an unvarnished, very accessible way.

Particularly interesting are the many points on which earlier tomes and conventional wisdom are mistaken. For instance, Mr. Feith demonstrates that the record simply does not support claims that: "Bush and his hawkish advisers" were intent on waging war on Iraq from the get-go; Donald Rumsfeld and his "neocons" failed to prepare for postwar Iraq and that the State Department had, only to have its plans spurned by the Pentagon; and Mr. Feith's office tried to manipulate prewar intelligence about Saddam's weapons of mass destruction. Given how central many of these myths are to criticism of the Iraq war, the contradictory evidence deserves attention.

Even more critical to this week's congressional testimony — and what follows on Capitol Hill, on the hustings and, not least in Iraq — are Mr. Feith's insights into problems that continue to afflict America's execution of the war. For example:

• On issue after issue, George W. Bush's decisions on Iraq were undermined by subordinates who opposed the president's policies. As Feith charitably puts it, Mr. Bush "could ... justly be faulted for an excessive tolerance of indiscipline, even of disloyalty from his own officials." This pattern continues with members of the intelligence community, senior diplomats and even, until recently, a top military officer routinely flouting presidential direction — sometimes openly, on other occasions through malicious leaks to the press.

• There has been an abject failure to address competently and comprehensively the ideological nature of our Islamofascist enemies and their enablers. "In the fight against terrorism, the effort to counter ideological support remains a gaping deficiency. No one in the administration... is currently developing and implementing a comprehensive strategy beyond public diplomacy."

• Most important, the costs of failures to act — or win in Iraq — continue to be underestimated. "If and when major new terrorist attacks occur in the United States, the public will re-examine the Bush administration strategy for the war on terrorism. The likely criticism then will not be that the president was too tough on the jihadists, the Ba'athists and other state supporters of terrorism, but that the administration might have fought the terrorist network even more intensely and comprehensively.

"No dereliction of statesmanship is as unpardonable as a failure to protect the nation's security. If the head of government underreacts when the country is threatened, history is not likely to excuse him on the grounds that his excessive caution enjoyed bipartisan support."

Doug Feith has made important contributions to our nation's security for three decades in public life and the private sector. If his splendid "War and Decision" gets the reading it warrants, others will be more likely to do so as well.