Was the invasion of Iraq, notwithstanding its unforeseen twists and turns, the right call? Have the American public and U.S. policy-makers taken the correct lessons from the war? How will history see it?

Invading Iraq proved to have been a mistake, and the management of the war was a series of blunders across several administrations, but the decision to invade wasn’t strategic folly or reckless hubris. There were legitimate reasons for invasion and no great alternatives, and the decision was made at a time when the trauma of 9/11 had left the president and his cabinet incredibly intolerant of risk.

Keeping Persian Gulf oil flowing was, and remains, a major American interest. It may not be essential for fueling the U.S. economy, but it is for maintaining a desirable price level and the global availability of oil, to which our prosperity continues to be linked (as we’ve been reminded by Saudi Arabia’s recent rejection of Biden-administration entreaties to pump more). Our reliance on oil necessitated our providing security to countries in the region — and it still should.

The precipitating reasons for invading Iraq in 2003 were three: the unsustainability of the continued stationing of U.S. forces in Saudi Arabia, the collapse of the economic-sanctions regime on Iraq, and the preservation of the international nuclear-weapons-nonproliferation regime.

The top grievance al-Qaeda used to justify its attacks on the Khobar Towers in 1996, the U.S. embassies in Nairobi and Dar es Salaam in 1998, the USS Cole in 2000, and our homeland in 2001 was the presence of U.S. troops in Saudi Arabia. The Saudis relied on the U.S. military for protection in part because Saddam Hussein’s invasion of Kuwait in 1990 had made countries in the region unsafe. They moved to improve their own militaries, but our obligations under the Carter Doctrine and Saddam’s threats, even after his defeat in the 1991 war, made removing U.S. troops from Saudi Arabia problematic.

That risk was compounded as managing Saddam by economic means was becoming untenable. The U.N. oil-for-food program was intended to provide for Iraq’s people while taking spoils out of Saddam’s reach, yet it was badly managed (half the participating companies paid bribes), and Saddam retained the ability to control the program’s beneficiaries. It hurt Saddam and elites loyal to him relatively little, and harm to average Iraqis was magnified, eroding international support for the program’s continuation. By 2002, allied governments were relaxing sanctions, weakening the prospect of nonmilitary pressure.

As the chief advocate and enforcer of the nuclear-nonproliferation regime, the U.S. also had an interest in preventing Iraq from acquiring nuclear weapons. Inspectors were shocked by how advanced Iraq’s nuclear program was revealed to be when inspections were made possible after the 1991 war (and before Saddam shut off access to them), and this raised their suspicions about possible clandestine elements of the program. The invasion demonstrated that we would not be deterred from attacking a country that had and had used chemical weapons and was, we believed, in possession of — or working hard to quickly develop — nuclear weapons.

The dearth of better options to manage the threats from Iraq is often glossed over by some who criticize the decision to invade. There’s one other factor that is often elided, which is both temporal and psychological but had strategic effect. I joined the Bush White House in the aftermath of the September 11 attacks, before which I had worked on Colin Powell’s joint staff and been a student of Condoleezza Rice. I was struck by the worry among the president’s senior team that every day could be another 9/11. We didn’t understand the dimensions of the problem and made a number of regrettable choices while we were learning the nature and magnitude of the threat, building the defenses to better shield the U.S. against its enemies, and applying military- and covert-operations pressure to keep enemies fearing for their lives.

Had the same problems regarding Iraq loomed even a couple of years later rather than in 2002–03, the Bush administration would have likely chosen to manage them differently. Fear skewed its risk tolerance. Subsequent administrations don’t have the same excuse for their own Iraq-policy mistakes.

The costs of the war in Iraq have outweighed its benefits. We missed so many opportunities to strengthen international participation. I’d have loved to see, for example, then-secretary Powell give a speech in Germany about the responsibilities free societies have to those suffering under authoritarianism, or make clear to our Gulf partners the limits of our availability if they chose not to participate in counterterrorism efforts, or use intelligence-sharing policies to keep accountable those profiting from the oil-for-food program. Much of the costs, though, have to do with the war’s management and our abandonment of Iraq after the 2007 troop surge. And the cost of our mistakes in Iraqi, American, and coalition lives ought to weigh on the conscience of all of us who had any role in the war.

But American policy-makers and the public have learned the wrong lessons from this experience — for instance, that successful counterinsurgency is impossible; that if we step back, allies will step forward and carry out policies similar to the ones we would have; that military force can’t solve problems (when in fact military force is how most international-security problems are solved, for good or ill); and that enduring until you achieve your political objectives constitutes the waging of “endless war.”

The lessons we ought to have taken away instead are that war-gaming with people knowledgeable about enemy culture and operational practice is essential; that warfare is not just about strength but also about adaptation; that diplomacy is successful only when backed by credible force; and, finally, that our enemies know that to defeat the U.S. they must keep fighting even when they’re losing — because, eventually, we’ll lose interest.