Bush finally acceded: America wasn’t going to kill its way out of this morass. A month after the field manual’s release, the president pinned a fourth star to Petraeus’s shoulder, gave him charge of all U.S. forces in Iraq and green-lit the surge. Petraeus named Mansoor his executive officer and tapped McMaster to lead his strategic-assessment team. The COINdinistas were insurgents no longer.

THE SURGE’S abiding relevance lies not in the operational realm but in the conceptual. It drew military and nonmilitary personnel into a state of mutual dependence, made protecting Iraqi civilians a central mandate and confronted the conflict’s political accelerants. Killing insurgents was subordinated to a new directive: making sure their ilk couldn’t return.

“We had a lot of military power on the ground to fight the insurgency,” Mansoor told me. “What we lacked was a robust, complimentary civilian effort to solidify the gains that the soldiers and marines were making on the streets of Iraqi cities and towns.” So General Petraeus and Ryan Crocker, the new ambassador in Baghdad, embedded provincial reconstruction teams (PRT) in combat units, filling their ranks with staff from USAID and the Departments of State, Agriculture and Justice. PRTs deployed to the front lines to tackle the socioeconomic drivers of the conflict. Soldiers and civilians put themselves at risk to secure and rebuild communities.

The surge gave warring factions breathing space, a narrow window for political accommodation. Stop shooting, start talking. But security provision alone couldn’t bring them to the table. In The Counterinsurgent’s Constitution, Ganesh Sitaraman argues that in small wars, the counterinsurgent must initiate reconstruction in the midst of the conflict. “Counterinsurgency embraces a bottom-up approach,” he writes, “that grows organically from the local conditions and context: the population’s capacities and needs, their traditions and preferences. Organic reconstruction reframes warfighting as village-building.” Sitaraman sees reconciliation programs as “weapons of war, instruments of lawfare that can be designed to reduce or even eliminate the insurgency.” At the height of the surge, an Army combat brigade and a civilian organization that Donald Trump now wants to defund put that theory to the test. Together, they weaponized reconciliation in the “Triangle of Death.”

Mahmudiya District, Baghdad’s ethnically mixed southern doorstep, earned its bleak moniker during the early years of the war. Assassinations, public beheadings, improvised explosive devices and armed banditry punctuated virulent sectarian warfare. “Not one man in a hundred will stand up to a real killer,” James Mattis once remarked to the author Bing West. “It’s ruthlessness that cows people.”

Col. Michael M. Kershaw was told a year ahead of time, far longer than usual, that his brigade would deploy to Mahmudiya. Early on in his preparation, he realized that “this was fundamentally a problem of counterinsurgency.” But it was not, contrary to the assumption I voiced to him during our interview, McMaster’s operations in Tal Afar that brought him to this conclusion. He wasn’t terribly chagrined at my mistake.

Kershaw and McMaster, it turns out, go way back. They were in the same West Point class, where they played rugby together and shared a course on revolutionary warfare. They were both company commanders in Iraq during the Gulf War. When Kershaw attempted to dabble in counterinsurgency in Afghanistan in 2003, McMaster noticed. Kershaw was leading the First Ranger Battalion in Kunar Province and discovered “the futility of trying to pick these guys off.” McMaster flew in and received a briefing from Kershaw’s second-in-command. When McMaster took COIN a few steps further in Tal Afar two years later, Kershaw was tracking his progress.

Kershaw and the Second Brigade of the Tenth Mountain Division arrived in Mahmudiya in August 2006. From the beginning, he said, he was determined to “harness something that would outlast our tour of duty.” The Triangle of Death’s new counterinsurgents manned neighborhood outposts, with an eye toward restoring community security. Special operators killed and captured Al Qaeda and its foreign fighters. Kershaw’s deputy, Lt. Col. John Laganelli, told me he worked to bring agricultural and economic-development capabilities into the region, “to create some form of normalcy for the people.” Meanwhile, the “Awakening” had moved from Anbar Province and was sweeping across Mahmudiya. Local Sunnis began betraying Al Qaeda, electing to supply the U.S. military with intelligence in exchange for pay and promises of safety.

In Kershaw’s telling, plenty of tribal leaders wanted to talk, but the Second Brigade was struggling to consolidate the ink dots of “awakened” locals into a big-picture compromise. There were too many moving pieces, too little trust: “We were trying to navigate an archipelago of societal islands. The campaign was like an island-hopping exercise.” And Kershaw was, by all accounts, the Army’s resident authority on south Baghdad. “I was the Mahmudiya expert,” he said matter-of-factly. “But man, I went to public school in east Texas. I could only scrape the surface. The language barrier. The culture barrier.” Someone in Kershaw’s orbit coined the term “sheikhapalooza” to denote the unproductive theatrics that characterized the military’s sit-downs with tribal leaders.

By the summer of 2007, the Second Brigade had expelled Al Qaeda and bloodied the remaining insurgent groups. A promising, yet tenuous, calm took hold. Fearing regression, Kershaw’s embedded PRT connected him with the United States Institute of Peace, a congressionally funded peacebuilding outfit—which the colonel “knew nothing about,” he’s still embarrassed to say. When he met with USIP staff in the Green Zone, “a lightbulb went off,” he told me. “Their set of capabilities was something we could not get elsewhere. They had Iraqis who could actually run the negotiations between the sheikhs. They could seat Iraqis with Iraqis.”

USIP’s objective, in its view, was to preempt revenge. Orchestrate a reconciliation process capable of suturing the ethnosectarian wounds the jihadists had wrought. Kershaw saw USIP in a utilitarian light: just as he turned to special-operations units to kill and capture irreconcilables, he turned to USIP to reconcile the rest. “Those were desperate times. We were looking for anyone with value added.” Desperate they were. There were almost 2,200 IED incidents during the Second Brigade’s fifteen-month tour. Fifty-four soldiers were killed in action. Kershaw was eager to maximize the returns on his soldiers’ costly investment. He didn’t need FM 3-24 or media-savvy Petraeus to teach him about civil-military innovation. But the new field manual and Petraeus’s public championing of counterinsurgency, Kershaw told me, did give his brigade the cover it needed to engage deeply with the people of his sector and keep Al Qaeda on the ropes. (McMaster actually came down to Mahmudiya during Kershaw’s deployment to visit his old friend and exchange ideas.)

USIP tapped into its reservoir of Iraqi intermediaries, whom the institute had for years been working with and training in conflict management. They worked closely with the Second Brigade to map out Mahmudiya’s intricate fault lines and volatile power centers. Which individuals and which clans were best positioned to convince their tribes to negotiate with bitter enemies? Kershaw’s soldiers went to great lengths to protect and shuttle USIP personnel—one such escort was struck by an IED. Sarhang Hamasaeed, USIP’s current director of Middle East programs, went out of his way to emphasize the complementary dynamic between the institute and the military. USIP wasn’t exactly in a position to rid Mahmudiya of Al Qaeda, he told me, but neither was the Army equipped to rebuild social cohesion.

USIP marshalled its acute expertise and capitalized on its ambiguous provenance. Despite having “United States” in its name, the institute was able to disassociate itself from the oft-reviled occupation (in Kershaw’s opinion, USIP’s Iraqi-led approach allowed it to function like “an NGO we fund as a front”). All the while, it was leveraging its pedigree in diverse corridors of power. Kershaw was constrained by chain of command; USIP was not. The institute collaborated with the State and Defense Departments to secure buy-in from integral power brokers at the municipal, provincial and national levels. Despite a hostile reception, USIP was able to extract an endorsement from officials in Prime Minister Nouri al-Maliki’s inner circle.

USIP meticulously cultivated a web of local mediators and Triangle of Death stakeholders. The resulting delegation possessed unparalleled insight into the competing interests and hidden motives of the aggrieved parties. USIP and its delegation turned their attention to Mahmudiya’s exiled Sunni leaders. Without them, the entire enterprise would grind to a halt. Post-Saddam Iraq had devastated their livelihoods and forced them to take refuge in Amman, Jordan. They held America responsible. Young firebrands and other radical elements in their tribes vied for influence. Some espoused sectarian warfare. Both Rusty Barber, USIP’s chief of party in Iraq at the time and an architect of the peacebuilding initiative, and Colonel Kershaw described the links between these exiles and Mahmudiya’s insurgents in cryptic terms. At the very least, Barber told me, they “were capable of operating as spoilers to any agreement they were left out of.” They “definitely had blood on their hands,” Kershaw said.

Among the delegates USIP recruited for the Amman mission was Ali al-Mufraji, a thirty-five-year-old general in the Iraqi army. He was the most senior Iraqi military officer in Mahmudiya and, in Kershaw’s experience, “the real power behind the throne,” a reference to the local Shia government. When Sens. Lindsey Graham and John McCain visited the sector, Kershaw suggested that they meet with Mufraji. In Amman, the one-star general’s job was to convince the exiles of the initiative’s viability, especially on security grounds. A Shia married to a Sunni, Mufraji’s pragmatism helped shift the tenor of the talks, which were nearly derailed by suspicion. The most formidable source of agitation was the widespread detention of Sunnis haphazardly branded as terrorist accomplices. Mufraji brandished his laptop, popped open a spreadsheet and revealed the status of tribesmen in custody. His candor and transactional efficiency fostered trust. The exiles accepted the project’s merits and, later, convinced Mahmudiya’s senior tribal leaders to participate in a Hail Mary dialogue. In a letter dated August 23, 2007, Kershaw credited USIP with “creating an atmosphere where real communication could take place” and implored the institute to see the project through.