The Iraq war pumped adrenaline into the publishing industry. First, journalists wrote accounts of their embedded experiences. These added color, but shed little light on the thinking that shaped the campaign. A second wave of books focused on what went wrong. Many of these were shoddy. Authors like David Phillips, Larry Diamond, and George Packer based their works on a narrow range of sources and filled gaps with questionable secondary accounts and, in Mr. Packer’s case, partisan blogs.

How refreshing it is then to read Michael Gordon and Lieutenant General Bernard Trainor’s “Cobra II: The Inside Story of the Invasion and Occupation of Iraq” (Pantheon, 603 pages, $27.95). Well-written, -documented, and cogent, it provokes thought, even if not always agreement. Mr. Gordon, chief military correspondent for the New York Times, and General Trainor, a retired Marine Corps general, combine their talents to weave a narrative of the Iraq campaign. They seek to explore “how a military campaign that was so successful in toppling Saddam Hussein’s regime set the conditions for the insurgency that followed.” Their work is broad and nuanced because they have won the trust of a far greater range of people than previous authors have. This is not the case with General Tony Zinni’s “The Battle for Peace: A Frontline Vision of America’s Power and Purpose” (Palgrave Macmillan, 233 pages, $24.95), a rambling polemic built on General Zinni’s disjointed observations about the nature of the military and the Middle East.

For understanding of Iraq, discard General Zinni. He neither did the groundwork nor provides the insight of “Cobra II.” Interviewing top policymakers, Mr. Gordon and General Trainor trace the story of the Iraq war to September 11, 2001. Al Qaeda may have perpetrated the attacks, but they were a symptom of a larger problem. In a speech now forgotten, Saddam gloated. It was a pivotal moment. According to Douglas Feith, the undersecretary of defense for policy, “[Defense Secretary] Rumsfeld understood that … we were not going to solve this problem by focusing narrowly on the perpetrators of 9/11.”

As the crosshairs centered on Saddam, debate raged about the resources required to wage war. Mr. Rumsfeld emphasized military transformation. With new technology, less could be more. United States Central Command commander General Tommy Franks dusted off Iraq contingency plans, of which there had been many. General Franks’s predecessor and mentor, General Zinni, had figured that securing Iraq would require nearly 400,000 troops. Mr. Rumsfeld suggested that General Franks should be able to do the job with 125,000 troops, a number Mr. Gordon and General Trainor suggest he pulled from thin air. The former speaker of the House, Newt Gingrich, described the relationship between the general and the secretary as one of “constant negotiation.” Mr. Rumsfeld won.

Still, the debate over troop strength permeates the narrative. On February 25, 2003, Senator Levin, a Democrat of Michigan, asked the Army chief of staff, Eric Shinseki, how many troops the Pentagon would need to secure Iraq. General Shinseki, who was not involved in the planning, opined that it would take “several hundred thousand.” Here further interviews could have helped elucidate the debate.Why did Mr. Levin publicly seek to disclose troop numbers on the eve of the operation, when planners worried Saddam might target vulnerable concentrations of forces in Kuwait? After liberation, more troops might have better secured Iraq’s frontiers, but Mr. Gordon and General Trainor do not explore how they could defeat a terrorist campaign based on car and suicide bombs. Nor do they speculate about whether more aggressive rules of engagement rather than increased troop numbers could have prevented looting.

Within planning circles, controversy raged not only over troop strength, but also over whether there should be an Iraqi face to the forces. While General Franks called Mr. Feith “the f-ing stupidest guy on the face of the earth,” in retrospect the general was more deserving of that description.As Centcom commander, he quashed General Wayne Downing’s proposal to use air power to protect a safe haven in which a free Iraqi army could rally. Then, in 2003, General Franks sought to quash attempts to train an Iraqi force, saying, “I don’t have time for this f-ing bullsh-.” Centcom’s foot-dragging and interagency rivalry hampered the program. When the insurgency began, the Free Iraqi Force was a shadow of its potential self.

Only after Saddam’s Fedayeen resisted the American advance did Centcom reconsider. General Franks then scrambled to find an Iraqi face, which he found in 700 volunteers gathered by Iraqi National Congress leader Ahmad Chalabi. But when Centcom flew them to Nasiriyah, it denied them arms and, initially, food and water. Here the authors’ account and analysis fall short. How did the Iraqis interpret their treatment? How would a more robust training program have eased the postwar security crisis?

Sometimes Mr. Gordon and General Trainor accept too uncritically the conventional wisdom of their Centcom sources. They imply that de-Baathification and the decision to disband the Iraqi army contributed to violence. But had the authors analyzed data rather than relying on interview spin, they might have found that insurgent violence was proportional to re-Baathification. Lieutenant General David Petraeus’s flaunting of de-Baathification orders in Mosul created short-term calm, but dangerous long-term insecurity.And criticism of the decision to disband the Iraqi army should be moot, since the army had evaporated weeks before. Again, neither Mr. Gordon nor General Trainor asks whether an Iraqi face would have salvaged pride and reversed the army’s evaporation.

Still, in this election year, perhaps the greatest value of “Cobra II” is laying bare myths and misrepresentations. It has become fashionable in intellectual circles to accuse President Bush of lying about the nature of Iraq’s arsenal. Mr. Gordon and General Trainor relate the real anxiety that permeated Centcom as American troops advanced on Baghdad. On April 2, 2003, American intelligence intercepted what it believed were orders for an Iraqi chemical attack. Likewise, the State Department’s Future of Iraq Project did not provide a viable plan for postwar Iraq. Its director, Tom Warrick, upset at being disciplined for misconduct, leaked this mischaracterization to journalists willing to bash the Bush administration.

The CIA’s venality permeates the narrative. Because the Langley Air Force base had trained its own covert Iraqi force, it sought to quash the Pentagon’s larger, overt program. A CIA case officer tried to sidetrack efforts to place an Iraqi face on the fight with a false report. The CIA station chief spoke against de-Baathification, wildly exaggerating the numbers of those affected. Still, there is too little attention to how the CIA’s war on the White House impacted the Iraq campaign. As a former Defense Intelligence Agency officer, Patrick Lang,told the American Prospect, “Of course they [the CIA] were leaking. … They’d say things like, ‘This last thing that came out, surely people will pay attention to that. They won’t re-elect this man [Bush].'”

Still, all of this does not let the Pentagon off the hook. The Kurdish leader (and current Iraqi president) Jalal Talabani had warned Mr. Rumsfeld about the potential for looting in an August 2002 meeting.

Looking back today, more than three years after the insurgency began, what went wrong? General Zinni’s paean to stability sheds little light. Before the war, containment had failed, and Saddam and his successor sons planned to reconstitute Iraq’s weapons program as soon as sanctions collapsed.Mr.Gordon and General Trainor suggest five shortcomings: misreading the foe, over-reliance on technology, failure to adapt to developments on the battlefield, dysfunctional American military structures, and the Bush administration’s disdain for national building. Each item on their list is valid.

But there are other factors the authors do not address.What was the cost of diplomacy? While war planning took 18 months, Condoleezza Rice’s fear that European diplomats would criticize post-war planning before U.N. diplomacy was exhausted delayed serious reconstruction planning until just weeks before the invasion. Equally important was the question of occupation. In order to win U.N. support, Secretary of State Powell acquiesced to the label of occupying power. For the sake of Turtle Bay endorsement, he undercut Iraqi partners and justified insurgent rhetoric.

Also absent from Mr. Gordon and General Trainor’s list is poor policy coordination. Here General Zinni is right: “A couple of the wrong kinds of personalities is all it takes to gum up the system.” Within the military, he briefly mentions bureaucratic rivalry between Centcom and the United States European Command that in the last decade undercut coordination in East Africa. Left unsaid is how the same division hampered policy toward Turkey in the run-up to Operation Iraqi Freedom. Though Mr. Gordon and General Trainor write about rivalry between the State and Defense Departments, why did the National Security Council fail to coordinate policy and enforce discipline over the process? How did Baathists and Islamists exploit American infighting to undercut Iraqi stability and security? Nor do the authors consider the role of the American press. While the press reflected events in Iraq, to what extent did Iraqi behavior reflect the press?

The ultimate study of Iraq will come when American documents are declassified, and captured Iraqi documents released.Until then,”Cobra II”sets the standard for serious analysis. “The Battle for Peace” is broader in its scope, but shallow. General Zinni may believe that stability trumps instability, but September 11 demonstrated that obsequiousness to Arab dictators does not make America more secure. Sometimes transformation is necessary; how to achieve it is the stuff of debate.

Mr. Rubin, editor of the Middle East Quarterly, is a resident scholar at the American Enterprise Institute.