Nowadays, few people step forth to speak well of the Iraq War, to own up to the support they gave that American campaign in the Arab world. Yet Operation Iraqi Freedom, launched 10 years ago this week, was once a popular war. We had struck into Afghanistan in 2001 to rout al Qaeda and the terrorists' Taliban hosts—but the 9/11 killers who brought ruin onto American soil were not Afghan. They were young Arabs, forged in the crucible of Arab society, in the dictators' prisons and torture chambers. Arab financiers and preachers gave them the means and the warrant for their horrific deeds.
America's previous venture into Iraq, a dozen years earlier, had been a lightning strike: The Iraqi dictator was evicted from Kuwait and then spared. Saddam Hussein's military machine was all rust and decay by 2003, but he swaggered and let the world believe that he had in his possession a deadly arsenal of weapons of mass destruction. The Arab redeemer, as he had styled himself, lacked the guile that might have saved him. A great military expedition was being readied against him in London and Washington, but he gambled to the bitter end that George W. Bush would not pull the trigger.
On the eve of Operation Iraqi Freedom—the first bombs fell on March 19—well over 70% of the American public supported upending the Saddam regime. The temptation to depict the war as George W. Bush's and Dick Cheney's is convenient but utterly false. This was a war waged with congressional authorization, with the endorsement of popular acceptance, and with the sanction of more than a dozen United Nations Security Council resolutions calling for Iraq's disarmament.
Those unburdened by knowledge of the ways of that region would come to insist that there had been no operational links between the Iraqi despot and al Qaeda. These newborn critics would insist on a distinction between secular terrorism and religious terrorism, but it was a distinction without a difference.
The rationale for the war sustained a devastating blow in the autumn of 2004 when Charles Duelfer, the chief U.S. arms inspector for Iraq, issued a definitive report confirming that Saddam had possessed no stockpiles of weapons of mass destruction. The war now stood on its own—and many of its former supporters claimed that this wasn't what they had signed up for. Yet the "architects" of the war could not pull the plug on it. They soldiered on, offering a new aim: the reform and freedom of Iraq, and the example of a decent Iraq in the "heart of the Arab world."
President Bush, seen in this image from television, addresses the nation from the Oval Office at the White House, on March 19, 2003. Bush said U.S. forces launched a strike against targets of military opportunity in Iraq, describing the action as the opening salvo in an operation to disarm Iraq and to free its people.
There were very few takers for the new rationale. In the oddest of twists, American liberalism now mocked the very idea that liberty could put down roots in an Arab-Muslim setting.
Nor were there takers, among those watching from lands around Iraq, for the idea of freedom midwifed by American power. To Iraq's east lay the Iranian despotism, eager to thwart and frustrate the American project. To the west in Syria there was the Baath dictatorship of the House of Assad. And beyond there was the Sunni Arab order of power, where America was despised for giving power to Shiites. For a millennium, the Shiite Arabs had not governed, and yet now they ruled in Baghdad, a city that had been the seat of the Islamic caliphate.
A stoical George W. Bush held the line amid American disaffection and amid the resistance of a region invested in the failure of the Iraq campaign. He doubled down with the troop "surge" and remained true to the proposition that liberty could stick on Arab soil.
There is no way of writing a convincing alternative history of the region without this war. That kind of effort is inherently speculative, subject to whim and preference. Perhaps we could have let Saddam be, could have tolerated the misery he inflicted on his people, convinced ourselves that the sanctions imposed on his regime were sufficient to keep him quarantined. But a different history played out. It delivered the Iraqis from a tyranny that they would have never been able to overthrow on their own.
The American disappointment with Iraq helped propel Barack Obama to power. There were strategic gains that the war had secured in Iraq, but Mr. Obama had no interest in them. Iraq was the "war of choice" that had to be brought to a "responsible close," he said. The focus instead would be on that "war of necessity" in Afghanistan.
A skilled politician, Mr. Obama made the Iraqi government an offer meant to be turned down—a residual American force that could hardly defend itself, let alone provide meaningful protection for the fledgling new order in Baghdad. Predictably, Iraq's rulers decided to go it alone as 2011 drew to a close. They had been navigating a difficult course between Iran and the U.S. The choice was made easy for them, the Iranian supreme leader was next door, the liberal superpower was in retreat.
Heading for the exits, Mr. Obama praised Iraqi Prime Minister Nouri al-Maliki as "the elected leader of a sovereign, self-reliant and democratic Iraq." The praise came even as Mr. Maliki was beginning to erect a dictatorship bent on marginalizing the country's Kurds and Sunni Arabs and even those among the Shiites who questioned his writ.
Two weeks ago, Stuart W. Bowen Jr., the special inspector general for Iraq reconstruction, issued his final report, called "Learning from Iraq." The report was methodical and detailed, interspersed with the testimonies of American and Iraqi officials. One testimony, by an Iraqi technocrat, the acting minister of interior, Adnan al-Asadi, offered a compelling image: "With all the money the U.S. has spent, you can go into any city in Iraq and you can't find one building or project built by the U.S. government. You can fly in a helicopter around Baghdad or other cities, but you can't point a finger at a single project that was built and completed by the United States."
It was no fault of the soldiers who fought this war, or of the leaders who launched it, that their successors lacked the patience to stick around Iraq and safekeep what had been gained at an incalculable cost in blood and treasure.
Mr. Ajami is a senior fellow at Stanford's Hoover Institution and the author, most recently, of "The Syrian Rebellion" (Hoover Press, 2012).