With Mosul, Iraq’s second-largest city, firmly under the control of a jihadi group so extreme that it was denounced by Al Qaeda; with government forces battling for Tikrit, the birthplace of Saddam Hussein; and with the religious leader of Iraq’s Shiites issuing a call to arms at Friday’s prayers, we have reached the moment that skeptics of the 2003 United States invasion warned about all along: the implosion of the country, and, possibly, the entire region. “The state of Iraq is in imminent collapse,” Faisal Istrabadi, formerly a senior Iraqi diplomat, said on Thursday.

President Obama and his military advisers are scrambling to come up with a response. Speaking on the South Lawn of the White House on Friday, Obama indicated that some sort of U.S. military action is likely, but he ruled out sending American troops, and he made clear that any U.S. involvement would be conditional on the Iraqi government of Nuri al-Maliki taking steps to unify the country. The United States does not want to be drawn back into a situation in which “while we are there we are keeping a lid on things,” but “as soon as we are not there, people act in ways that are not conducive to the long-term interests of the country,” Obama said.

Having withdrawn almost all U.S. forces from Iraq in 2011—there are still a few Marines there, protecting the U.S. Embassy in Baghdad and other sites—the President is in a tight spot. From his body language, it is clear that he wants to reëngage with Iraq about as much as he wants to undergo a root canal. Most Americans feel the same way. But, given the huge investment of manpower, money, and prestige that the United States has invested in the country over the past decade, it would be a brave or foolhardy President who’d simply step aside and watch the fighters of the Islamic State of Iraq and al-Sham overrun Baghdad.

Elsewhere in Washington, the blame game has already begun. “This is the education of Barack Obama, but it’s coming at a very high cost to the Syrian people to the Iraqi people, to the American national interest,” Doug Feith, the Under-secretary of Defense for Policy from 2001 to 2005, told Politico. “The President didn’t take seriously the warnings of what would happen if we withdrew and he liked the political benefits of being able to say that we’re completely out.” Senator John McCain, whom the President telephoned on Friday, has called on Obama to fire his entire national-security team, claiming, “Could all of this have been avoided? The answer is absolutely yes.”

McCain is right; it could have been avoided. If, in the aftermath of 9/11, President George W. Bush had treated the arguments of Feith, McCain, and other advocates of the Iraq War with the disdain they deserved, we (and the Iraqis) wouldn’t be where we are today.

If, in the immediate aftermath of the U.S. invasion, Paul Bremer, the American proconsul in Baghdad, and his boss, Donald Rumsfeld, had not decided to disband Saddam’s army, the one institution that somewhat unified the country, the Iraqi state would be stronger. If, in addition, Bremer and Rumsfeld had ordered enough U.S. troops onto the streets to preserve order, then Iraq might (and it’s only a might) have held together peacefully instead of degenerating into sectarianism, anarchy, and violence.

If Prime Minister Maliki, whom the United States eventually settled on as its favored Iraqi leader, had made a serious effort to reach out to the Sunnis and the Kurds, rather than acting like a sectarian ward heeler, the departure of U.S. forces might not have created the political stalemate and institutional power vacuum that the jihadis, first in Anbar Province and now in Nineveh and Saladin, have exploited.

None of these things happened, but the greatest mistake was the initial one. In invading Iraq and toppling Saddam, the Bush Administration opened Pandora’s Box. Given what has happened since 2003, it is almost comical to read the prewar prognostications of the neocons and paleocons for what would happen after Saddam was gone. There was talk of turning Iraq into a democratic model for other Middle Eastern countries—making it another Turkey, or even a Jordan, with a Hashemite restoration. Today it is faced with the prospect of a bloody dismemberment into three sectarian mini-states: the Sunnis in the west and northwest; the Kurds in the northeast; and the Shiites in the center and the oil-rich south. (It’s unclear where Baghdad, a city divided along religious lines, fits into this picture.)

The irony is painfully acute. Eleven years ago, in response to a terrorist attack by a group of anti-American religious fanatics, the United States invaded an Arab country with hardly any jihadis, or very few of them, to overthrow a secular dictator. Today, with much blood and money having been spent, northern and western Iraq is full of jihadis, and the U.S. government is figuring out how to prevent them from overrunning the rest of the country.

The Obama Administration isn’t entirely blameless. The President, in ordering the pullout of the remaining U.S. troops in 2011, after negotiations with the Maliki government about the terms for maintaining a small force had broken down, was betting that the Iraqi Army, with some American arms and the continued assistance of American military contractors and trainers, would be able to defend the country. “After all, there will be some difficult days ahead for Iraq, and the United States will continue to have an interest in an Iraq that is stable, secure, and self-reliant,” Leon Panetta, the Secretary of Defense, said at the time.

Some U.S. military commanders and civilian officials, including McCain, were skeptical of the Obama Administration’s strategy. Reporting on the order to withdraw, Mark Landler, of the Times, wrote, “American military officials had wanted a ‘residual’ force of as many as tens of thousands of soldiers to remain past 2011 as an insurance policy against future violence. Those numbers were scaled back, but the expectation was that 3,000 to 5,000 American troops would remain. Some top American military officials were dismayed by the decision, saying Mr. Obama was putting the best face on a breakdown in tortured negotiations with the Iraqis.”

Some White House officials insisted at the time—and still insist—that there was no realistic prospect of keeping even a modest U.S. force in Iraq; the Maliki government wanted all the U.S. troops out, and it refused to make any concessions, declining, for example, to countenance legal immunity for American military trainers. And even if the Pentagon had kept a few thousand troops on bases in Iraq, it’s far from clear that their presence would have been sufficient to prevent the ISIS fighters from spilling over the border from Syria and destabilizing things.

In the coming days and weeks, the October, 2011, decision, which had the overwhelming support of the American public, will be relitigated. That’s a legitimate debate to have. But it shouldn’t be allowed to distract from the broader truth, which is that Iraqis and the rest of us are still living with the consequences of the initial determinations made by President Bush, Vice-President Dick Cheney, and their colleagues.

The Iraq invasion and occupation was ill-conceived, ill-executed, and ill-fated. It had terrible consequences not just for Iraq but for many other countries. It illustrated the limits of American military power—the opposite of what it was intended to do—and it helped accomplish what Osama bin Laden could never have achieved on his own: drawing the United States and its allies into an open-ended global battle with militant Islam. When you hear Feith and other architects of the Iraq invasion criticizing Obama for cutting and running, it is well to remember that.

Photograph by Ahmed Saad/Reuters.