Skinner became increasingly consumed by the incongruity between his words and his actions. He felt like a “fraud,” he said. He preached that insurgencies arose out of the failure of local policing, yet he didn’t know a thing about the gangs operating a few blocks away. “We have people that are disappearing into the cracks of society,” he said. And they can be helped only on an individual basis. “Then you have to scale that support to a neighborhood. And then to a city.”

Because local police departments pay poorly, “the people who have been trained to do this work best are never going to be doing it,” Skinner said. According to a study by Brown University, since 2001 the average American taxpayer has contributed more than twenty-three thousand dollars to veterans’ care, homeland security, and military operations in Syria, Iraq, Afghanistan, and Pakistan. “I used to spend more money on meals and entertainment for a couple of sources in Amman, each year, than the Savannah Police Department has to spend on cars,” Skinner told me. “And whatever the American people got out of my meals in Amman had way less impact on their lives than what was happening down the block.”

In October, 2016, one of Skinner’s closest friends in the C.I.A. was killed by isis forces in Afghanistan. Skinner was despondent. A few months later, he left the Soufan Group and joined his local police force, taking a pay cut of more than a hundred thousand dollars a year.

For the Savannah police, the biggest obstacle in gaining the community’s trust is the city’s history. Savannah is around fifty-five per cent black, and Georgia practiced segregation well into the second half of the twentieth century; after Skinner completed his training, he was startled to find that many interactions he had with older black men began with them reflexively putting up their hands.

Georgia’s first black police officer was sworn in on May 3, 1947. His name is John Alliston White, and, along with eight other black officers, he joined Savannah’s police force as part of what the local papers called “an experiment,” overseen by a sympathetic lieutenant named Truman Ward. “The other white officers—they used to call him ‘the nigger Jesus,’ ” White told me.

White, who is ninety-three, is the only surviving member of the original nine. I met him at his house, and we spent an afternoon poring over faded photographs, yellowed newspaper clippings, and memorabilia that filled his living-room cabinets and hung from his walls.

White attended high school in Cuyler-Brownsville, an area of Savannah that, after emancipation, was set aside for black families. In spite of Jim Crow laws, by the early twentieth century it had a thriving, educated black middle class, made up of doctors, lawyers, teachers, and, later, civil-rights advocates.

For more than a decade, White and the other black officers were not allowed to arrest white people or use the drinking fountain at the police barracks. Several of his white colleagues hazed him, and, when his shift was over, they sometimes hired a cleaner to wash the interior of the car he had used, “because they said that we were dirty,” he told me. His first couple of years on the force nearly drove him to suicide. “We went through hell,” he said.

According to White, in the nineteen-sixties a new chief started requiring officers to write reports. “The black officers—we were educated,” White said. Some of the white officers couldn’t write, and many of the more racist cops left the force. White became a detective, and when Martin Luther King, Jr., came to Savannah he served as his bodyguard. But, when people took to the streets after King’s assassination, White was forced to become the “principal arresting officer for eight hundred and seven demonstrators,” he recalled; his superiors thought that it would be better if white cops were not involved.

By the seventies, according to Jamal Touré, a professor at Savannah State University, many middle-class black families were moving out of Cuyler-Brownsville. With desegregation, Touré told me, “we start saying, ‘Oh, we can now go into these other neighborhoods,’ ” leaving behind the poor and working-class people. Houses were abandoned, and, as explicitly racist laws were replaced with policies that led to the mass incarceration of black men, neighborhoods began to collapse. “The larger historical sweep of the experience of black Americans with the government of the United States and its arms of authority, like the police, is one of out-and-out white supremacy,” David M. Kennedy, the criminologist, told me. “The law was used to control and abuse black communities.” Cuyler-Brownsville, crippled by desperation and blight, soon became consumed by gang violence.

John White retired in 1984. He told me that, throughout his career, the police force was plagued by corruption. By the early eighties, drug dealers were transporting pot and cocaine on shrimping boats from South America to the islands east of Savannah, and officers on the drug task force were taking a cut.

By the early nineties, Savannah had one of the highest murder rates in the United States. In 2013, with corruption, theft, and sexual-harassment scandals brewing in the ranks, Willie Lovett, the chief of police, abruptly retired, and was later arrested and convicted on extortion, gambling, and obstruction charges, for colluding with illegal gambling networks. He is currently in federal prison.

Lovett’s replacement was Jack Lumpkin, a forty-eight-year veteran of Georgia policing, who, as a young black officer, had been forced to service white officers’ cars. Lumpkin had spent more than thirty years in leadership positions, and was known throughout the state for his single-strike policy on lying. He soon fired a number of officers. Others quit on their own. “We were wondering when they were going to actually start learning that lying was a cardinal sin,” Lumpkin told me, smiling. The department aggressively recruited new cops who Lumpkin believed would develop more “legitimacy with the citizens,” and partnered with the National Network for Safe Communities, led by Kennedy, in an attempt to reduce neighborhood gang shootings.

According to Kennedy, neighborhood gang violence, which accounts for most of the shootings in Savannah, is driven not only by small-group dynamics, the availability of weapons, and obsessions with vendettas but also by alienation from authorities. “It’s a fundamental break in the social contract,” he said. “If you’re in trouble, you have to take care of it yourself, because you can’t ask the police for help. So that becomes another shooting.” In high-crime areas, he continued, “the networks of perpetrators are essentially the same as the networks of victims.”

In Savannah, neighborhoods with vastly different demographics and crime rates are often separated by only the width of a street. North of a Confederate monument in Forsyth Park, tourists walk through the historic district, lined with cafés, antique shops, and grand antebellum homes, oblivious to the poverty a few blocks away. I stayed at the Marshall House, built in 1851, which keeps a well-lit portrait of Robert E. Lee over the staircase, near a framed copy of Georgia’s Ordinance of Secession. The city’s historic-tour guides tend to gloss over slavery, as if it were impolite to acknowledge the violence and oppression behind the construction of everything beautiful. Just west of the old city center, the housing office in Yamacraw Village—a public-housing facility, home to many poor African-Americans—is a replica of the big house on the Hermitage Plantation.

One night last fall, someone reported a rape at the corner of Forty-fifth and Florance, in the heart of Cuyler-Brownsville. Skinner raced to the intersection, and found a young white couple sitting on the grass, buttoning their pants. They were hopelessly drunk and lost. The woman said that they had taken a taxi from a bar downtown but that it had dropped them off there instead of at her house, in the affluent Ardsley Park neighborhood. Skinner laughed. “Does this look like fucking Ardsley Park to you?” he asked.

The woman lowered her voice to a whisper. “I don’t want to be racist, but—”

“But you’re gonna be, aren’t you?”

“There are a lot of black people.”

The police lights had woken people in nearby houses. Skinner called another taxi. As the couple waited on the corner, a middle-aged black woman ambled over, dressed in pajamas. “Oh, I see,” she said, raising her eyebrows. “We can’t walk around their neighborhood, but they can fuck in our yards.”

One night in late December, at around 3:30 a.m., a few blocks south of Cuyler-Brownsville, a young black man ran into the road and urged Skinner to pull over. He said that he’d been at the home of a girl he “hangs out with,” and either she had stolen his watch or he had misplaced it—he wasn’t sure. He reeked of alcohol, and couldn’t remember the woman’s name or address, but he gestured in the direction of the housing projects a few blocks over. Skinner asked for the man’s name and date of birth, to run a quick check for outstanding warrants. “Anthony,” the man said, before hesitating and adding “Greene” and a date of birth.

Skinner drove around the block. “He definitely just gave me a fake last name,” he told me. “People don’t usually lie about their first name.” Skinner pulled over and typed “Anthony Greene” into a police database on his onboard laptop. No record. Then he tried “Anthony” and the man’s date of birth, and found “Anthony Jackson,” who had been charged with dozens of crimes, including lying to police officers about his identity, and jailed at least thirty times. The photograph on the screen showed the man we had just met. In a corner of the screen, there was a small notification: “Alias: Anthony Greene.” Jackson was on probation, but he didn’t have an outstanding warrant, and, apart from apparently lying to Skinner, he hadn’t done anything wrong.

Skinner returned to the corner, and explained to Jackson that he couldn’t find the watch without knowing where the woman lived. Jackson nodded and thanked him. “Listen, buddy, next time don’t give me a fake name, O.K.?” Skinner said.

“I didn’t!” Jackson called out. “I got an I.D.” He stumbled into the road, handed Skinner his driver’s license, and shouted his Social Security number.

“God damn it, he just couldn’t help it,” Skinner muttered. If the driver’s license was fake, he’d have to arrest him. But a different database showed that the license was authentic, and that it belonged to Anthony Greene. And yet a search of the Social Security number he had given Skinner led straight back to Anthony Jackson.

“He’s his own legal doppelgänger!” Skinner exclaimed. “He’s two people, but neither of them is wanted—which is insane, because literally everyone in this neighborhood is wanted.” After a few minutes of cross-checking databases, he walked back to the man, returned his license, and apologized.

In the next few days, Skinner kept bringing up the case. “Imagine if he had been belligerent, or there was a warrant out for one of him,” he said. “We had all the time in the world. But, even with these vast databases of information, we came out of that interaction with zero knowledge. Maybe negative knowledge.” He shook his head. “We’ve invaded countries on worse information. But, if the C.I.A. taught me one thing, it is to always be acutely aware of the tremendous amount of shit I don’t know.”