Months of ground work were to culminate in a conference at Baghdad’s Al-Rashid Hotel. The Army provided organizers and participants with transportation and employed robust measures to protect the hotel itself. Rusty Barber told me that General Petraeus personally redirected funds to the reconciliation process.

The three-day conference began on October 16. USIP crafted the format and agenda. The institute’s Iraqi facilitators conducted the proceedings. They instructed participants in mediation techniques without besmirching their traditions. A few verbal altercations boiled over, but were promptly cooled. By day two, the community leaders had reached consensus on goals and corresponding action items, which USIP channeled into a draft accord overnight. On the third day, pugnacious debate over the final text yielded “Mahmoudiya: Cornerstone for Peace and National Accord,” a concrete framework for the reconstruction of the district. Thirty-one Shia and Sunni tribal leaders, so recently warring, signed the document in view of Iraqi and foreign press. The pact’s symbolic value wasn’t lost on Kershaw. To him, its impact was simple: “It legitimized the ‘Awakening.’” Stop shooting, start talking was officially socially acceptable. Al Qaeda had lost its local base of support.

Violence declined precipitously. The 101st Division’s Third Brigade, which replaced Kershaw’s, lost a single soldier during its deployment. The Army trimmed its presence from a brigade combat team of 3,500 to a battalion of 650. The entire USIP project cost American taxpayers around $1.5 million, roughly the price of a single Tomahawk cruise missile. On February 11, 2009, Petraeus praised “USIP’s on-the-ground peacebuilding efforts” in a letter to the Office of Management and Budget. In it, he singled out the Mahmudiya initiative as “a striking success story.” The pact has endured the Arab Spring and the rise of ISIS. It holds to this day.

THE INTENTION here is not to wax poetic about how the mighty COINdinistas injected thirty thousand troops into Iraq, saved the day and galloped off into the sunset. Petraeus has been mythologized too often. The military historian Douglas Porch, Petraeus’s harshest critic, titled his scathing polemic Counterinsurgency Myths. Even sympathetic observers point to Petraeus’s preoccupation with his own glory and his cunning in spinning self-serving narratives.

Nor is it reasonable to paper over U.S. killing. Brought back to Iraq to oversee strategy during the surge, McMaster was vehement that some insurgents had too much blood on their hands to be politically accommodated. Under Lt. Gen. Stanley McChrystal, Joint Special Operations Command took scores of these irreconcilables, including Abu Musab al-Zarqawi, off the battlefield. But McChrystal opted for the scalpel whenever possible. His kill-and-capture missions were designed to be discriminate. Collateral damage would only breed more terrorists.

Besides, controlling territory is not the jihadist’s only concern. Al Qaeda and ISIS inflict the deepest wounds on the virtual battlefield. A suicide bombing at a market has little military value; it resonates as “propaganda of the deed.” ISIS recruits foreign fighters and radicalizes homegrown terrorists online. Viral, emotive images are its weapons of choice. And as Graeme Wood argues in The Way of the Strangers, ISIS’s weaponization of theology cannot simply be dismissed as a bastardization of Islam.

Mending social cohesion in Iraqi communities, therefore, is only part of the story. Suffice it to say, the combination of the surge and the “Awakening”—the widespread Sunni uprising against Al Qaeda, underway before Petraeus took over—dramatically reduced violence. From 2004 to mid-2007, more than 1,500 civilians died every month in Iraq. By December 2007, that number plummeted to five hundred. From June 2008 to June 2011, around two hundred civilians died every month.

The military could not occupy Iraq forever. America failed to establish a sustainable political order before withdrawing. Communities lacked closure, and tensions gestated. Maliki’s overt hostility toward the Sunnis stoked discord and violence. ISIS exploited these divisions, co-opted Sunni tribes who once fought alongside the Americans and, in short order, routed the Iraqi army. In June 2014, ISIS declared a caliphate over a broad swathe of territory. At its peak, it controlled 40 percent of Iraq.

In Washington, reluctance to intervene understandably found voice. The Iraq War scarred America. Words like “quagmire” are never far from the lips of those who advocate for retrenchment. The Iraq War is as politically corrosive as ever, a reliable dog whistle that incites rabid denunciations of hegemonic overreach and paternalistic democracy promotion. But Iraq is more than just a trope. The decision to invade, among the worst foreign-policy blunders in U.S. history, and the prosecution of the war are two different things. Conflating counterinsurgency with the neoconservative worldview—just because they have Iraq in common—is reductive. Petraeus and McMaster did, in fact, make common cause with neocon stalwarts like Eliot A. Cohen and Frederick W. Kagan as they labored to convince President Bush to change tack. They were playing the hand they were dealt. Neocons broke Iraq; Petraeus and McMaster were tasked with putting it back together. Trump himself seems amenable to this sentiment. In March, he told Haider al-Abadi, Iraq’s moderate prime minister, “We shouldn’t have gone in, but certainly we shouldn’t have left.”

Jettisoning the lessons of the Iraq War for fear of striking a political nerve would be feckless. Gaslighting the COINdinistas would be cataclysmic.

DONALD TRUMP is in an unenviable predicament. He’s got to defeat ISIS and prevent its resurgence, with a footprint small enough to repel allegations of interventionism. The Pentagon wants to retain U.S. forces in Iraq for years after Mosul is recaptured. “I believe it’s in our national interest that we keep Iraqi security forces in a position to keep our mutual enemies on their back foot,” Defense Secretary Mattis told Senate leaders in late March. “I don’t see any reason to pull out again and face the same lesson.”

The White House has since delegated new authorities to the Defense Department to decide how many troops are deployed in the war against ISIS. Two Pentagon officials made clear to me that Operation Inherent Resolve is a conventional military affair. Adrian J. T. Rankine-Galloway, a Pentagon spokesperson, used some version of “supporting role” five times in our brief exchange. I asked about the day after Mosul falls. “The government of Iraq is responsible for governance and security matters within its territory,” the Marine Corps major responded. A second Pentagon official, this one senior, spoke to me on condition of anonymity. “Once ISIS is defeated, you still have sectarian tensions and divisions. That’s where soft power comes into play,” the official said. Gutting civilian agencies, like Trump has proposed, would “hinder the U.S. ability to prevent insurgencies before they happen.” Surely there’s some middle ground between full-tilt counterinsurgency and what Major Rankine-Galloway referred to as “supporting local partners as those forces liberate territory from ISIS control.”

The lessons the COINdinistas took from Iraq in the 2000s extend beyond that time and place. In Waging Insurgent Warfare, Seth G. Jones conducts an empirical study on the 181 insurgencies that took form between World War II and 2015. Insurgency prevention across the board, he demonstrates, hinges on ameliorating local grievances, “particularly ones associated with low per capita income, ethnic polarization, and religious polarization.” Washington isn’t going to “fix” Iraq in one fell swoop. But Trump cannot afford to defund the organizations doing a measure of good. Michael Singh, managing director at the Washington Institute for Near East Policy, was once responsible for George W. Bush’s national-security policy toward the region stretching from Morocco to Iran. “How we defeat ISIS is just as important as whether we do,” he told me. “We need to leave behind conditions in Iraq both for effective local governance and stable regional geopolitics. It will be worth taking our time to get this right.”

If America is going to prolong putting uniformed men and women in harm’s way, dipping deeper and deeper into the war chest, common sense demands that the administration maximize their impact. If America is going to help Iraq break the endless cycle of sectarian violence—undoubtedly, a prerequisite for hindering an embarrassing ISIS comeback—it will have to find a cost-effective, palatable means of translating battlefield triumphs into political progress. What Trump needs is a force multiplier. Regrettably, the White House’s recent budget proposal sentenced to death an indispensable variable in that equation.

Seven years after Mahmudiya, the United States Institute of Peace executed another unlikely scheme, in the northern city of Tikrit.

Tikrit in 2014 was like Tal Afar in 2005, but worse. Ravaged by calculating jihadists, Saddam Hussein’s ancestral hometown collapsed on itself. ISIS has a vested interest in instability; internecine violence is basically insurgent catnip. Camp Speicher had been home to a few thousand Iraqi military cadets before ISIS weeded out 1,700 Shia, slaughtered them and dumped their bodies into mass graves. It released photos and videos to adorn its sickening propaganda. The Speicher victims represented twenty southern tribes, from nine provinces. By the time a hodgepodge of Iraqi Security Forces and Iran-linked militias ejected ISIS from Tikrit in April 2015, the massacre had been seared into Shia memory.