Even soldiers who fight wars from a safe distance have found themselves traumatized. Could their injuries be moral ones?

An MQ-9 drone in a sun shade at Creech Air Force Base in Nevada.CreditDina Litovsky/Redux, for The New York Times

In the spring of 2006, Christopher Aaron started working 12-hour shifts in a windowless room at the Counterterrorism Airborne Analysis Center in Langley, Va. He sat before a wall of flat-screen monitors that beamed live, classified video feeds from drones hovering in distant war zones. On some days, Aaron discovered, little of interest appeared on the screens, either because a blanket of clouds obscured visibility or because what was visible — goats grazing on an Afghan hillside, for instance — was mundane, even serene. Other times, what unspooled before Aaron's eyes was jarringly intimate: coffins being carried through the streets after drone strikes; a man squatting in a field to defecate after a meal (the excrement generated a heat signature that glowed on infrared); an imam speaking to a group of 15 young boys in the courtyard of his madrasa. If a Hellfire missile killed the target, it occurred to Aaron as he stared at the screen, everything the imam might have told his pupils about America's war with their faith would be confirmed.

The infrared sensors and high-resolution cameras affixed to drones made it possible to pick up such details from an office in Virginia. But as Aaron learned, identifying who was in the cross hairs of a potential drone strike wasn't always straightforward. The feed on the monitors could be grainy and pixelated, making it easy to mistake a civilian trudging down a road with a walking stick for an insurgent carrying a weapon. The figures on-screen often looked less like people than like faceless gray blobs. How certain could Aaron be of who they were? "On good days, when a host of environmental, human and technological factors came together, we had a strong sense that who we were looking at was the person we were looking for," Aaron said. "On bad days, we were literally guessing."

Initially, the good days outnumbered the bad ones for Aaron. He wasn't bothered by the long shifts, the high-pressure decisions or the strangeness of being able to stalk — and potentially kill — targets from thousands of miles away. Although Aaron and his peers spent more time doing surveillance and reconnaissance than coordinating strikes, sometimes they would relay information to a commander about what they saw on-screen, and "60 seconds later, depending on what we would report, you would either see a missile fired or not," he said. Other times, they would trail targets for months. The first few times he saw a Predator drone unleash its lethal payload — the camera zooming in, the laser locking on, a plume of smoke rising above the scorched terrain where the missile struck — he found it surreal, he told me. But he also found it awe-inspiring. Often, he experienced a surge of adrenaline, as analysts in the room exchanged high-fives.

Aaron's path to the drone program was unusual. He grew up in Lexington, Mass., in a home where red meat and violent video games were banned. His parents were former hippies who marched against the Vietnam War in the 1960s. But Aaron revered his grandfather, a quiet, unflappable man who served in World War II. Aaron also had a taste for exploration and tests of fortitude: hiking and wandering through the woods in Maine, where his family vacationed every summer, and wrestling, a sport whose demand for martial discipline captivated him. Aaron attended the College of William & Mary in Virginia, where he majored in history, with a minor in business. A gifted athlete with an air of independence and adventurousness, he cut a charismatic figure on campus. One summer, he traveled to Alaska alone to work as a deckhand on a fishing boat.

During Aaron's junior year, in 2001, he woke up one morning to a phone call from his father, who told him that the twin towers and the Pentagon had been attacked. Aaron thought instantly of his grandfather, who served for three years as a military police officer on the European front after the attack on Pearl Harbor. He wanted to do something similarly heroic. A year later, after spotting a pamphlet at the William & Mary career-services office for the National Geospatial-Intelligence Agency, a national-security agency that specializes in geographical and imagery analysis, he applied for a job there.

Aaron began working as an imagery analyst at the N.G.A. in 2005, studying satellite pictures of countries that had no link to the war on terror. Not long after he arrived, an email circulated about a Department of Defense task force that was being created to determine how drones could help defeat Al Qaeda. Aaron answered the call for volunteers and was soon working at the Counterterrorism Airborne Analysis Center. He found it exhilarating to participate directly in a war he saw as his generation's defining challenge. His pride deepened as it became clear that the task force was having a significant impact and that the use of drones was increasing.

Aaron spent a little over a year at the task force, including several months in Afghanistan, where he served as the point of contact between the drone center in Langley and Special Forces on the ground. After this, he worked for a private military contractor for a while. In 2010, an offer came from another contractor involved in the drone program to serve as an imagery-and-intelligence analyst. But as Aaron mulled the terms, something strange happened: He began to fall apart physically. The distress began with headaches, night chills, joint pain. Soon, more debilitating symptoms emerged — waves of nausea, eruptions of skin welts, chronic digestive problems. Aaron had always prided himself on his physical fitness, but suddenly he felt frail. Working for the contractor was out of the question. "I could not sign the paperwork," he said. Every time he sat down to try, "my hands stopped working — I was feverish, sick, nauseous."

Aaron went back to Lexington to live with his parents and try to recuperate. He was 29 and in the throes of a breakdown. "I was very, very unwell," he told me. He consulted several doctors, none of whom could specify a diagnosis. In desperation, he experimented with fasting, yoga, Chinese herbal medicine. Eventually, his health improved, but his mood continued to spiral. Aaron couldn't muster any motivation. He spent his days in a fog of gloom. At night, he dreamed that he could see — up close, in real time — innocent people being maimed and killed, their bodies dismembered, their faces contorted in agony. In one recurring dream, he was forced to sit in a chair and watch the violence. If he tried to avert his gaze, his head would be jerked back into place, so that he had to continue looking. "It was as though my brain was telling me: Here are the details that you missed out on," he said. "Now watch them when you're dreaming."

It has been almost 16 years since a missile fired from a drone struck a Toyota Land Cruiser in northwest Yemen, killing all six of its passengers and inaugurating a new era in American warfare. Today, targeted killings by drones have become the centerpiece of U.S. counterterrorism policy. Although the drone program is swathed in secrecy — the C.I.A. and the military share responsibility for it — American drones have been used to carry out airstrikes in at least eight different countries, analysts believe. Over the past decade, they have also provided reconnaissance for foreign military forces in half a dozen other countries. According to the Bureau of Investigative Journalism, a London-based organization that has been tracking drone killings since 2010, U.S. drone strikes have killed between 7,584 and 10,918 people, including 751 to 1,555 civilians, in Pakistan, Afghanistan, Yemen and Somalia. The U.S. government's figures are far lower. It claims that between 64 and 116 noncombatants outside areas of active hostilities were killed by drones between 2009 and 2016. But as a report published last year by the Columbia Law School Human Rights Clinic and the Sana'a Center for Strategic Studies noted, the government has failed to release basic information about civilian casualties or to explain in detail why its data veers so significantly from that of independent monitors and NGOs. In Pakistan, Somalia and Yemen, the report found, the government officially acknowledged just 20 percent of more than 700 reported strikes since 2002.

"Kill chain" operations expanded under Barack Obama, who authorized roughly 500 drone strikes outside active conflict zones during his presidency, 10 times the number under George W. Bush. (This number does not include strikes carried out in Iraq, Afghanistan and Syria.) These operations have continued to grow under President Trump, who oversaw five times as many lethal strikes during his first seven months in office as Obama did during his last six months, analysts believe. According to the Bureau of Investigative Journalism, last year U.S. airstrikes more than tripled in Yemen and Somalia, where the Trump administration circumvented restrictions on operations outside war zones that were put in place in 2013. The administration has also made these operations even less transparent than under Obama, who received widespread criticism on this score.

The escalation of the drone wars has been met with strikingly little congressional or popular opposition. Unlike the policy of capturing and interrogating terrorism suspects that was adopted after Sept. 11, which fueled vigorous debate about torture and indefinite detention, drone warfare has been largely absent from public discourse. Among ordinary citizens, drones seem to have had a narcotizing effect, deadening the impulse to reflect on the harm they cause. Then again, the public rarely sees or hears about this harm. The sanitized language that public officials have used to describe drone strikes ("pinpoint," "surgical") has played into the perception that drones have turned warfare into a costless and bloodless exercise. Instead of risking more casualties, drones have fostered the alluring prospect that terrorism can be eliminated with the push of a button, a function performed by "joystick warriors" engaged in an activity as carefree and impersonal as a video game. Critics of the drone program have sometimes reinforced this impression. Philip Alston, the former United Nations special rapporteur on extrajudicial executions, warned in 2010 that remotely piloted aircraft could create a "PlayStation mentality to killing" that shears war of its moral gravity.

But the more we have learned about the experiences of actual drone fighters, the more this idea has been revealed as a fantasy. In one recent survey, Wayne Chappelle and Lillian Prince, researchers for the School of Aerospace Medicine at Wright-Patterson Air Force Base in Fairborn, Ohio, drew on interviews that they and other colleagues conducted with 141 intelligence analysts and officers involved in remote combat operations to assess their emotional reactions to killing. Far from exhibiting a sense of carefree detachment, three-fourths reported feeling grief, remorse and sadness. Many experienced these "negative, disruptive emotions" for a month or more. According to another recent study conducted by the Air Force, drone analysts in the "kill chain" are exposed to more graphic violence — seeing "destroyed homes and villages," witnessing "dead bodies or human remains" — than most Special Forces on the ground.

Because the drone program is kept hidden from view, the American public rarely hears about the psychic and emotional impact of seeing such footage on a regular basis, day after day, shift after shift. Compared with soldiers who have endured blasts from roadside bombs — a cause of brain injuries and PTSD among veterans of the wars in Iraq and Afghanistan — the wounds of drone pilots may seem inconsequential. But in recent years, a growing number of researchers have argued that the focus on brain injuries has obscured other kinds of combat trauma that may be harder to detect but can be no less crippling. Drone warfare hasn't eliminated these hidden wounds. If anything, it has made them more acute and pervasive among a generation of virtual warriors whose ostensibly diminished stress is belied by the high rate of burnout in the drone program.


An Air Force sensor operator practicing on drone flight simulators at Creech Air Force Base.CreditDina Litovsky/Redux, for The New York Times

As the volume of drone strikes has increased, so, too, have the military's efforts to attend to the mental well-being of drone warriors. Last year, I visited Creech Air Force Base in Nevada to interview drone pilots about their work. Forty minutes north of Las Vegas, Creech is a constellation of windswept airstrips surrounded by sagebrush and cactus groves. It is home to some 900 drone pilots who fly missions with MQ-9 Reapers in numerous theaters. Creech also has a group of embedded physiologists, chaplains and psychologists called the Human Performance Team, all of whom possess the security clearances required to enter the spaces where drone pilots do their work, in part so that they can get a glimpse of what the pilots and sensor operators experience.

A psychologist on the team named Richard (who, like most of the airmen I spoke to, asked to be identified by only his first name) told me that, two weeks into the job, he poked his head into a ground control station just as the crew was "spinning up for a strike." A veteran of the Marine Corps, he felt a surge of adrenaline as he watched the screen flash. Then he put the incident out of mind. A few weeks later, he was at his son's band concert, and as the national anthem played and he peered up at the Stars and Stripes, the memory came back. "I'm looking up at the flag, but I could see a dead body," he said. He was shaken, but he couldn't say anything to his family because the operation was classified.

Drone warriors shuttle back and forth across such boundaries every day. When their shifts end, the airmen and women drive to their subdivisions alone, like clerks in an office park. One minute they are at war; the next they are at church or picking up their kids from school. A retired pilot, Jeff Bright, who served at Creech for five years, described the bewildering nature of the transition. "I'd literally just walked out on dropping bombs on the enemy, and 20 minutes later I'd get a text — can you pick up some milk on your way home?" Bright enjoyed serving in the drone program and believed that he was making a difference, a sentiment I heard repeatedly at Creech. But other airmen in his unit struggled to cope with stress, he said — there were divorces and some cases of suicide.

Unlike office-park employees, drone operators cannot reveal much about how their day went because of classification restrictions. Unlike conventional soldiers, they aren't bolstered by the group solidarity forged in combat zones. Richard told me that when he was in the Marines, "there was a lot of camaraderie, esprit de corps." Although service members at Creech can get close to their co-workers, at the end of every shift they go home, to a society that has grown increasingly disconnected from war.

Before the drone personnel at Creech make their way home, some drop by the Airman Ministry Center, a low-slung beige building equipped with a foosball table, some massage chairs and several rooms where pilots and sensor operators can talk with clergy. A chaplain named Zachary told me that what most burdened the airmen he spoke to was not PTSD; it was inner conflicts that weighed on the conscience. He mentioned one pilot he met with, who asked, "I'm just curious: What is Jesus going to say to me about all the killing I've done?" Despite their distance from the battlefield, drone operators' constant exposure to "gut-wrenching" things they watched on-screen — sometimes resulting directly from their own split-second decisions, or conversely, from their inability to act — could cause them to lose their spiritual bearings and heighten their risk of sustaining a very different kind of battle scar: what some psychologists, as well as Zachary, have described as a "moral injury."

The term is not new. It appeared in the 1994 book "Achilles in Vietnam," by the psychiatrist Jonathan Shay, who drew on Homer's epic war poem the "Iliad" to probe the nature of the wounds afflicting veterans of the Vietnam War. Shay read the "Iliad" as "the story of the undoing of Achilles' character," which, he argued, unravels when his commander, Agamemnon, betrays his sense of "what's right," triggering disillusionment and the desire "to do things that he himself regarded as bad." Experiencing such disillusionment might not seem as traumatic as coming under enemy fire or seeing a comrade die. Shay disagreed. "I shall argue what I've come to strongly believe through my work with Vietnam veterans: that moral injury is an essential part of any combat trauma," he wrote. "Veterans can usually recover from horror, fear and grief once they return to civilian life, so long as 'what's right' has not also been violated."

Fifteen years later, the term "moral injury" began to appear more frequently in the literature on the psychic wounds of war, but with a slightly different meaning. Where Shay emphasized the betrayal of what's right by authority figures, a new group of researchers expanded the focus to include the anguish that resulted from "perpetrating, failing to prevent or bearing witness to acts that transgress deeply held moral beliefs," as a 2009 article in the journal Clinical Psychology Review proposed. In other words, they defined it as a wound sustained when soldiers wading through the fog of war betrayed themselves, through harmful acts they perpetrated or watched unfold. This definition took shape against the backdrop of the wars in Iraq and Afghanistan, chaotic conflicts in which it was difficult to distinguish between civilians and insurgents, and in which the rules of engagement were fluid and gray.

One author of the Clinical Psychology Review article was Shira Maguen, a researcher who began to think about the moral burdens of warfare while counseling veterans at a PTSD clinic in Boston. Like most V.A. psychologists, Maguen was trained to focus on the aftershocks of fear-based trauma — I.E.D. blasts that ripped through soldiers' Humvees, skirmishes that killed members of their unit. The link between PTSD and such "life-threat" events was firmly established. Yet in many of the cases she observed, the source of distress seemed to lie elsewhere: not in attacks by the enemy that veterans had survived, but in acts they had committed that crossed their own ethical lines. "I was hearing about experiences where people killed and they thought they were making the right decision," Maguen told me recently, "and then they found out there was a family in the car."

To find out how heavy the burden of killing actually was, Maguen, who is now a staff psychologist at the V.A. Medical Center in San Francisco, began combing through databases in which veterans of conflicts dating back to the Vietnam War were asked if they had killed someone while in uniform. In some cases, the veterans were also asked whom they killed — combatants, prisoners, civilians. Maguen wanted to see if there might be a relationship between taking another life and debilitating consequences like alcohol abuse, relationship problems, outbursts of violence, PTSD. The results were striking: Even when controlling for different experiences in combat, she found, killing was a "significant, independent predictor of multiple mental health symptoms" and of social dysfunction.

In San Francisco, Maguen convened groups where veterans came together and talked about the killing they had done. In the V.A. no less than in the military, this was a taboo subject, so much so that clinicians often refer to it euphemistically, if at all. The veterans in Maguen's groups didn't speak much about fear and hyperarousal, emotions linked to PTSD. Mostly, they expressed guilt and self-condemnation. "You feel ashamed of what you did," one said. Others described feeling unworthy of forgiveness and love. The passage of time did little to diminish these moral wounds, Maguen found. Geographic distance didn't lessen them much either. She recounted the story of a pilot who was haunted by the bombs he had dropped on victims far below. What troubled him was, in fact, precisely his distance from them — that instead of squaring off against the enemy in a fair fight, he had killed in a way that lacked valor. Obviously not all pilots felt this way. But the story underscored the significance of something Maguen has come to regard as more important than proximity or distance in shaping moral injury — namely, how veterans made sense of what they had done. "How you conceptualize what you did and what happened makes such a big difference," she said. "It makes all the difference."

The meaning and magnitude of moral injury remains contested. "It is not widely accepted by the military or the psychological community," Wayne Chappelle, of the School of Aerospace Medicine at Wright-Patterson Air Force Base, told me, adding that he did not believe it was prevalent among drone operators. This was somewhat surprising, because Chappelle was an author of the study revealing that many drone warriors struggled with lasting negative emotions after strikes, feeling "conflicted, angry, guilty, regretful." But the idea that war may be morally injurious is a charged and threatening one to many people in the military. Tellingly, Chappelle described moral injury as "intentionally doing something that you felt was against what you thought was right," like the wanton abuse of prisoners at Abu Ghraib. The definition used by researchers like Maguen is at once more prosaic and, to the military, potentially more subversive: Moral injury is sustained by soldiers in the course of doing exactly what their commanders, and society, ask of them.

By the time I met Christopher Aaron (whose given last name was left out of this article at his request), he had spent several years recuperating from his experience in the drone program. We first talked in a pub, not far from where he was living at the time. Aaron is now 37, with thick dark hair and a muscular build. He has a calm, Zen-like bearing, honed in part through yoga and meditation, but there was a trace of worry in his eyes and a degree of circumspection in his voice, particularly when he was pressed for details about particular missions (he emphasized that he could not talk about anything classified). At the pub, we spoke for two hours and agreed to continue talking over lunch the next day, so that he could pace himself. On my way to that appointment, my cellphone rang. It was Aaron, calling to reschedule. Our meeting the previous day had triggered a flood of anxiety, aggravating the pain in his back during the night.

Some analysts immediately feel that their work has left an emotional residue. In Aaron's case, the feeling unfolded gradually, coinciding with a shift in worldview, as his gung-ho support for the "war on terror" gave way to growing doubts. The disillusionment crept up in stages, starting, he realized in retrospect, a few months after he returned from Afghanistan. Although he felt proud of the work he did to help establish the drone program, he also started to wonder when the war's objective was going to be achieved. It was around this time that his manager asked him if he wanted to obtain resident C.I.A. employment status and become a career intelligence officer, which required taking a lie-detector test used to screen employees. Aaron said yes, but halfway through the test, after losing circulation in his arms and feeling hectored by the questions, he got up and abruptly left. The next day, Aaron told his manager that he had reconsidered.

Aaron ended up taking a trip to California instead, renting a motorcycle and riding all the way up the coast to Alaska, where he spent a week at a monastery on a small island, sleeping in a wood-framed chapel surrounded by spruce trees. Aaron grew up attending an Eastern Orthodox church, and the experience was faith-reaffirming. When he went back to the East Coast, he felt refreshed. But he was also out of money, so he went back to work in a field where he could easily land a job, with a military-and-intelligence contractor.

The former drone intelligence analyst Christopher Aaron at his home. ''I was very, very unwell,'' he said.CreditDina Litovsky/Redux, for The New York Times

By now, Aaron's idealism had waned. It receded further when, at the end of 2008, the contractor sent him back to Afghanistan. The first time he was there, in 2006, the war on terror seemed to be hastening the defeat of Al Qaeda and the Taliban. Now it seemed to Aaron not only that progress had stalled, but that things were sliding backward. "We were actually losing control of vast areas of the country," he said, even as the number of drone strikes was "four or five times higher" than before. The escalation under President Obama had begun.

As it happened, Aaron had taken with him to Afghanistan a copy of George Orwell's "1984." He had read the book in high school and, like most people, remembered it as a dystopian novel about a totalitarian police state. This time, what stuck in his mind was a book-within-the-book written by Emmanuel Goldstein, the rumored leader of the resistance, titled "The Theory and Practice of Oligarchical Collectivism." In the book, Goldstein describes the onset of a "continuous" war, waged by "highly trained specialists" on the "vague frontiers" of Oceania — an opaque, low-intensity conflict whose primary purpose was to siphon off resources and perpetuate itself. ("The object of waging a war is always to be in a better position in which to wage another war," Orwell writes.) Aaron had an eerie sense that a perpetual war was exactly what the "war on terror" was becoming.

As his disillusionment deepened, events that Aaron dismissed before as unavoidable in any war began to weigh more heavily on him. He recalled days when the feed was "too grainy or choppy" to make out exactly who was struck. He remembered joking with his peers that "we sometimes didn't know if we were looking at children on the ground or chickens." He also thought back to the times when he would be asked "to give an assessment of a compound where they had suspicion — there was fill-in-the-blank low-level Taliban commander in a remote region in the country. And we had seen other people come in and out of the same compound over the course of the preceding two or three days. They come and say: We're getting ready to drop a bomb on there — are there any people other than the Taliban commander in this compound? I'd just say 'no' because they don't want to hear 'I don't know.' And then two days later, when they have the funeral procession in the streets that we could observe with the Predators, you'd see as opposed to carrying one coffin through the streets they're carrying three coffins through the streets."

Aaron kept his misgivings mainly to himself, but his friends noticed a change in him, among them Chris Mooney, who picked him up at the airport when he returned from Afghanistan in 2009. He and Aaron had been friends since college, when Aaron exuded confidence and enthusiasm. "He was magnetic," Mooney said. At the airport, Mooney could scarcely recognize his friend. His affect was flat, his face a solemn mask. They went to dinner, where, at one point, a patron who overheard them talking came up to Aaron to thank him for his service. Aaron thanked him back, Mooney said, but in a muted tone. Mooney didn't press him for details, but he knew that something was seriously wrong. "It wasn't the same guy," he said.

The renewed interest in moral injury can be viewed as an effort to revisit the ethical issues that have been latent in our narratives of war all along — and to address sources of trauma that some veterans and military analysts recognized years ago, before the "war on terror" had even begun. In the influential 1995 book "On Killing," Dave Grossman, a retired Army lieutenant colonel and former professor of psychology at West Point, drew on historical studies and the personal accounts of ex-combatants to argue that the psychological costs of close-range killing were often devastating. The novels and memoirs of veterans were populated with characters haunted by such incidents. In Tim O'Brien's "The Things They Carried" (1990), for example, the narrator confesses that he can't shake the image of the Vietnamese man he killed on a footpath with a grenade — his body splayed, blood glistening on his neck. Later, the narrator indicates that he didn't actually kill the man, but he was there and watched him die, "and my presence was guilt enough." Literature could evoke the inner conflicts that played on loop in the minds of veterans tormented by their troubled consciences.

In the early 1970s, some psychiatrists listened to soldiers talk about such incidents at "rap groups" organized by Vietnam Veterans Against the War. Until this point, soldiers bearing psychic wounds tended to be dismissed by the military as cowards and malingerers. ("Your nerves, hell — you are just a goddamned coward," Gen. George S. Patton snapped at a soldier in a hospital during World War II.) The Yale psychiatrist Robert Jay Lifton, who sat in on the V.V.A.W. rap groups and wrote about the disfiguring effects of killing and participating in atrocities in his 1973 book, "Home From the War," helped to recast these veterans as sympathetic figures. Lifton argued that these former soldiers were burdened not by cowardice but by the guilt and rage they felt about their involvement in a misbegotten war. In his view, moral and political questions were inseparable from Vietnam veterans' psychic wounds, to the point that he believed activism to end the war could lessen their guilt and foster healing.

When PTSD was officially recognized in the Diagnostic and Statistical Manual of Mental Disorders, in 1980, many hoped it would lead society to reckon more honestly with the ethical chaos of war. The first definition included not only survivor's guilt but also guilt "about behavior required for survival" among the potential symptoms, language that addresses acts soldiers perpetrated that went against their own moral codes. Over time, however, the moral questions that animated reformers like Lifton were reduced to "asterisks in the clinician's handbook," notes the veteran David Morris in his book, "The Evil Hours," as military psychologists shifted attention to brain injuries caused by mortar attacks and roadside bombs. One reason for this may be that focusing on such injuries, and on harmful acts in which veterans were the victims, was more comfortable for the military. Another is that it may be more comfortable for V.A. clinicians, who weren't trained to address veterans' moral pain and who "may unknowingly provide nonverbal messages that various acts of omission or commission in war are too threatening or abhorrent to hear," noted the authors of the 2009 article on moral injury in Clinical Psychology Review. Avoiding such conversations was untenable with service members returning from Iraq and Afghanistan, who were enmeshed in messy counterinsurgency campaigns that often involved close-range killing and noncombatants. According to Brett Litz, a clinical psychologist at Boston University and an author of the 2009 article, "35 percent of the traumatic events that led soldiers to seek treatment for PTSD in a recent study were morally injurious events."

When the drone program was created, it seemed to promise to spare soldiers from the intensity (and the danger) of close-range combat. But fighting at a remove can be unsettling in other ways. In conventional wars, soldiers fire at an enemy who has the capacity to fire back at them. They kill by putting their own lives at risk. What happens when the risks are entirely one-sided? Lawrence Wilkerson, a retired Army colonel and former chief of staff to Colin Powell, fears that remote warfare erodes "the warrior ethic," which holds that combatants must assume some measure of reciprocal risk. "If you give the warrior, on one side or the other, complete immunity, and let him go on killing, he's a murderer," he said. "Because you're killing people not only that you're not necessarily sure are trying to kill you — you're killing them with absolute impunity."

Langley Air Force Base in Virginia is home to part of the 480th Intelligence, Surveillance and Reconnaissance Wing, a unit of 6,000 "deployed in place" cyberwarriors. They work on what is known as the "ops floor," a dimly lit room equipped with computers streaming footage from drones circling over numerous battlefields. Many of the enlistees arrayed around the screens are in their 20s and might pass for stock traders or Google employees were it not for their military boots and combat fatigues. But the decisions they make have far weightier consequences. According to a recent study by a team of embedded Air Force researchers who surveyed personnel at three different bases, nearly one in five I.S.R. analysts said they "felt directly responsible for the death of an enemy combatant" on more than 10 occasions. One analyst told the researchers, "Some of us have seen, read, listened to extremely graphic events hundreds and thousands of times."

"Over all, I.S.R. personnel reported pride in their mission, particularly supporting successful protection of U.S. and coalition forces," the survey found. But many also struggled with symptoms of distress — emotional numbness, difficulty relating to family and friends, trouble sleeping and "intrusive memories of mission-related events," including "images that can't be unseen."

As at Creech, steps have been taken to try to mitigate the stress: shorter shifts, softer lighting, embedded chaplains and psychologists. Counteracting this is the workload, which has escalated as drones have assumed an increasingly central role in the battle against ISIS and other foes. According to Lt. Col. Cameron Thurman, who was then the unit's surgeon general, the number of acknowledged missile strikes ordered by Central Command in the United States rose substantially between 2013 and mid-2017, even as the size of the work force has remained unchanged. "You've got the same number of airmen doing the same number of mission hours but with a 1,000-percent increase in those life-and-death decisions, so of course their job is going to get significantly more difficult," he said. "You're going to have more moral overload."

A bald man with a blunt manner, Thurman sat across from me in a windowless conference room whose walls were adorned with posters of squadrons engaged in remote combat operations. Also in the room was Alan Ogle, a psychologist who was an author of the recent survey of the 480th Wing. On the PTSD scale, Ogle said, members of the unit "didn't score high," owing to the fact that few had been exposed to roadside bombs and other so-called life-threat events. What seemed to plague them more, he told me, were some forms of "moral injury."

Two members of the I.S.R. Wing described to me how changed they were by their work. Steven, who had a boyish face and sensitive eyes, is originally from a small town in the South and joined the military straight out of high school. Four years later, he told me, he no longer reacted emotionally to news of death, even after his grandmother recently died. The constant exposure to killing had numbed him. "You're seeing more death than you are normal things in life," he said. He watched countless atrocities committed by ISIS. During one mission, he was surveilling a compound on a high-visibility day when 10 men in orange jumpsuits were marched outside, lined up and, one by one, beheaded. "I saw blood," he said. "I could see heads roll." Ultimately, though, what troubled him most was not bearing witness to vicious acts committed by enemy forces but decisions he had made that had fatal consequences. Even if the target was a terrorist, "it's still weird taking another life," he said. Distance did not lessen this feeling. "Distance brings it through a screen," he said, "but it's still happening, and it's happening because of you."

Another former drone operator told me that screens can paradoxically magnify a sense of closeness to the target. In an unpublished paper that he shared with me, he called this phenomenon "cognitive combat intimacy," a relational attachment forged through close observation of violent events in high resolution. In one passage, he described a scenario in which an operator executed a strike that killed a "terrorist facilitator" while sparing his child. Afterward, "the child walked back to the pieces of his father and began to place the pieces back into human shape," to the horror of the operator. Over time, the technology of drones has improved, which, in theory, has made executing such strikes easier, but which also makes what remote warriors see more vivid and intense. The more they watch targets go about their daily lives — getting dressed, playing with their kids — the greater their "risk of moral injury," his paper concluded.

In a hangar at Creech Air Force Base.CreditDina Litovsky/Redux, for The New York Times

This theory is echoed by Maguen's findings. In one study, she discovered that Vietnam veterans who killed prisoners of war had especially high rates of trauma. Maguen believes the reason is that the victims were not strangers to them. "When someone is a prisoner of war, you get to know them," she explained, "you have a relationship with them: You are watching them, you are talking to them. It may be that with drone operators, they also know their subjects fairly well: They have watched them, so there's a different kind of relationship, an intimacy."

For Christopher Aaron, the hardest thing to come to terms with was that a part of him had enjoyed wielding this awesome power — that he'd found it, on some level, exciting. In the years that followed, as his mood darkened, he withdrew, sinking into a prolonged period of shame and grief. He avoided seeing friends and had no interest in intimate relationships. He struggled with "quasi-suicidal" thoughts, he told me, and with facing the depth and gravity of his wounds, a reckoning that began in earnest only in 2013, when he made his way to the Omega Institute, in Rhinebeck, N.Y., to attend a veterans' retreat run by a former machine-gunner in Vietnam.

The weather was rainy and overcast. The discussion groups he sat in on, where veterans cried openly as they talked about their struggles, were no more uplifting. But for the first time since leaving the drone program, Aaron felt that he didn't have to hide his true feelings. Every morning, he and the other veterans would begin the day by meditating together. At lunch, they ate side by side in silence, a practice called "holding space." In the evenings, he drifted into a deep sleep, unperturbed by dreams. It was the most peaceful sleep he'd had in years.

At the Omega Institute, Aaron struck up a friendship with a Vietnam veteran from Minnesota, whom he later invited up to Maine. In the fall of 2015, at this friend's suggestion, he went to a meeting of the Boston chapter of Veterans for Peace. Soon thereafter, he began to talk about funeral processions he'd witnessed after drone strikes where more coffins appeared than he expected, first with members of the group, later at some interfaith meetings organized by peace activists. It was painful to dredge up these memories; sometimes his back would seize up. But it was a form of social engagement that he found deeply relieving.

At one interfaith meeting, Aaron mentioned that he and his colleagues used to wonder if they were playing a game of "whack-a-mole," killing one terrorist only to see another pop up in his place. He had come to see the drone program as an endless war whose short-term "successes" only sowed more hatred in the long term while siphoning resources to military contractors that profited from its perpetuation. On other occasions, Aaron spoke about the "diffusion of responsibility," the whirl of agencies and decision makers in the drone program that make it difficult to know what any single actor has done. This is precisely the way the military wants it, he suspects, enabling targeted killing operations to proceed without anyone feeling personally responsible. If anything, he felt an excess of remorse and culpability, convinced that targeted killings had very likely made things worse.

Peter Yeomans, a clinical psychologist who trained with Shira Maguen, has developed an experimental treatment for moral injury rooted in the sharing of testimonials, initially at weekly meetings where veterans come together to talk among themselves, and later at a public ceremony that the participants invite members of the community to attend. One goal of the treatment is to help veterans unburden themselves of shame, Yeomans told me. Another is to turn them into moral agents who can deliver the truth about war to their fellow citizens — and, in turn, broaden the circle of responsibility for their conduct.

In early May, I attended a ceremony in a small chapel on the third floor of the V.A. Medical Center in Philadelphia, where Yeomans now works. Seated on a stage in the chapel were a number of veterans, among them a wiry man with an unkempt brown beard who sat with his eyes closed and his hands folded in his lap. His name was Andy, and when invited to speak, he told the audience that he grew up in a violent home where he watched his older brother and baby sister endure abuse, which made him want to "protect the defenseless." After high school, he enlisted in the military and became an intelligence operative in Iraq. One night, on a mission near Samarra, a city in the "Sunni triangle," a burst of sustained gunfire erupted from the second-story window of a house, and Andy said he "called air" to deliver a strike. When the smoke cleared from the leveled home, there was no clear target inside. "I see instead the wasted bodies of 19 men, eight women, nine children," Andy said, choking back tears. "Bakers and merchants, big brothers and baby sisters.

"I relive this memory almost every day," he went on. "I confess to you this reality in the hope of redemption, that we might all wince and marvel at the true cost of war."

The room fell silent as Andy went back to his chair, sobbing. Then Chris Antal, a Unitarian Universalist minister who ran the weekly meetings with Yeomans, invited members of the audience to form a circle around the veterans who had spoken and deliver a message of reconciliation to them. Several dozen people came forward and linked arms. "We sent you into harm's way," began the message that Antal recited and that the civilians encircling the veterans repeated. "We put you into situations where atrocities were possible. We share responsibility with you: for all that you have seen; for all that you have done; for all that you have failed to do," they said. Later, members of the audience were invited to come forward again, this time to take and carry candles that the veterans had placed on silver trays when the ceremony began. Andy's tray had 36 candles on it, one for each person killed in the airstrike that he called in.

Yeomans and Antal told me over dinner afterward that they believe audience participation in the ceremony was crucial. Moral injury, they pointed out, is as much about society's avoidance and denial as it is about the ethical burdens that veterans bear. Antal added that, in his opinion, grappling with moral injury requires reckoning with how America's military campaigns have harmed not only soldiers but also Iraqis and civilians in other countries.

For Antal, broadening the scope to include these civilians is both a spiritual mission and a personal one. He bears a moral injury of his own, sustained when he was serving as an Army chaplain in Afghanistan. While there, he attended transfer ceremonies in which the coffins of fallen U.S. soldiers were loaded onto transport planes to be sent home. During one such ceremony, held at Kandahar Airfield, Antal noticed drones taking off and landing in the distance, and felt a flicker of conscience. The contrast between the dignity of the ceremony, during which the fallen soldier's name was solemnly announced as "Taps" was played, and the secrecy of the drone campaign, whose victims were anonymous, jarred him. "I felt something break," he told me. In April 2016, he resigned his commission as a military officer, explaining in a letter to President Obama that he could not support a policy of "unaccountable killing" that granted the executive branch the right to "kill anyone, anywhere on earth, at any time, for secret reasons."

The secrecy of the drone program makes it riskier for people who have served in it to share their stories. Jesselyn Radack, a lawyer for national-security whistle-blowers who has worked with Aaron, told me that several former drone operators she represents have suffered retaliation for talking about their experiences (she said one client had his house raided by the F.B.I. and was placed under criminal investigation after speaking on camera to a filmmaker). After Aaron began speaking publicly about his own past, someone hacked into his email and his cellphone, and a stream of anonymous threats began flooding his inbox. The hostile messages, calling him "scum" and warning him to "shut his big blabbermouth," were also sent to his father, whose email was likewise hacked. The barrage of threats eventually prompted Aaron to hire a lawyer to try to identify who was behind the harassment (the attorney he is working with, Joe Meadows of Bean Kinney & Korman, specializes in internet defamation), and to contact both the F.B.I. and the police.

The experience left Aaron shaken. But in recent months, he has begun to recover. He is now gainfully employed as an analyst of gold and other precious metals, a hobby he has turned into a vocation. He has started to reach out again to friends like Chris Mooney. He lives with his dog, a German shepherd, which he likes to take on walks through the forests near his home. His physical pain has mostly gone away, thanks in part to the regimen of yoga and meditation that he maintains. He still has his share of violent dreams, he told me. But he appears to have recaptured what for many years he had lost — his sense of moral purpose and, oddly enough, clarity, which is why he feels more ready to continue speaking publicly about his experience.

Not long ago, Aaron was invited to speak at an event organized by a branch of the Mennonite Church titled "Faithful Witness in a Time of Endless War." It took place on the campus of a school in Lansdale, Pa., in a small auditorium whose stage was festooned with peace quilts. Aaron approached the lectern in a brown blazer, with a somber expression. He reached forward to adjust the mic and thanked the event's organizers for inviting him to tell his story. Before sharing it, he asked for a moment of silence, "for all of the individuals that I killed or helped to kill."

Eyal Press is a journalist who has spent the past year as a fellow at the New York Public Library's Dorothy and Lewis B. Cullman Center for Scholars and Writers. He is at work on a book about people whose jobs take them into morally treacherous situations.