“Wars are fought on physical terrain—deserts, mountains, etc.—as well as on what they call ‘human terrain.’ Human terrain is essentially the social aspect of war, in all its messy and contradictory forms. The ability to navigate human terrain gives you better intelligence, better bomb-targeting data, and access to what is essentially a public relations campaign for the allegiance of the populace.”

Soldiers on both sides in Afghanistan must win the hearts and minds of local populations. A victory over a piece of territory may cause so much trouble for civilians that the larger battle is lost. If the fighting causes problems for a village or injures or kills some who live there, residents may overlook the new construction, water lines, and other benefits provided by the outsiders and rise against them.

“I once asked O’Byrne to describe himself as he was then. ‘Numb,’ he said. ‘Wasn’t scared, wasn’t happy, just fucking numb. Kept to myself, did what I had to do. It was a very weird, detached feeling those first few months.’ ‘You weren’t scared of dying?’ ‘No, I was too numb. I never let my brain go there. There were these boundaries in my brain, and I just never let myself go to that spot.’”

O’Byrne’s platoon is in the center of the worst fighting in Afghanistan. With daily firefights, troops dying, and blistering heat, the stress level is overwhelming; the men do what they can to stay alive and sane. It takes time for the platoon to coalesce fully, coordinate, and begin to fight efficiently; until then, tension and uncertainty have the upper hand.

“We’re getting hit from the east and the south and the west and the guy to the west is putting rounds straight through the position. They’ve got another guy below us in the draw and Olson is trying to deal with that but the SAW won’t angle low enough to hit him. ‘TOUGH LOVE!’ one man shouts; I’m pretty sure another starts singing. My brain has sought refuge in some slow-motion default that doesn’t allow for much decision-making, but after half a minute things regain their normal speed […].”

Intense firefights do strange things to the human mind, which sometimes reacts to overwhelming stress by distancing itself while the body does the work. Some men thrill to the sensation; others burn off stress later by smoking cigarettes, joking around, playing music, and even masturbating.

“A Third Squad team leader named Hijar ran forward to help, and he and Moreno managed to drag Guttie behind cover before anyone got hit. By that time the medic, Doc Old, had gotten to them and was kneeling in the dirt trying to figure out how badly Guttie was hurt. Later I asked Hijar whether he had felt any hesitation before running out there. ‘No,’ Hijar said, ‘he’d do that for me. Knowing that is the only thing that makes any of this possible.’”

In war, everyone depends on their teammates for survival. They become tight-knit and supremely reliable, risking themselves for the others, knowing that to fail in that duty is unpardonable, and to let a squad member suffer or die is unbearable. That loyalty isn’t simply practical: It’s emotional, in that the men are bonded together in a shared purpose against a common danger, which makes the other’s life as important as one’s own. Some may hate each other, but they’d die for each other.

“There are different kinds of strength, and containing fear may be the most profound, the one without which armies couldn’t function […].”

Soldiers do a variety of things to stanch their fear. Most hide it from the others; some ramp up emotionally and revel in battle; some sing or joke while firing; some get grumpy and matter-of-fact. They all must punch through the fear, or the battle is lost.

“Mobility has always been the default choice of guerrilla fighters because they don’t have access to the kinds of heavy weapons that would slow them down. The fact that networks of highly mobile amateurs can confound—even defeat—a professional army is the only thing that has prevented empires from completely determining the course of history.”

Second Platoon and the other American units in Korengal Valley face constant harassment from guerrilla teams who pepper them with gunfire, fade into the hills, then return the next day and repeat. It’s a time-honored technique of resistance forces: Make the invaders miserable all the time.

“I realized how easy it was to go from the living to the dead: one day you hear about some guy getting killed out at [Firebase] Vegas and the next day you’re that same guy for someone else.”

War is chancy, and death shows up unexpectedly. It’s unnerving to chat with someone in a war zone, then learn later that they’ve been killed. The feeling is disorienting: The guy was so alive yesterday, and now he’s in a body bag. Then you realize that you could be next.

“There is choreography for storming Omaha Beach, for taking out a pillbox bunker, and for surviving an L-shaped ambush at night on the Gatigal. The choreography always requires that each man make decisions based not on what’s best for him, but on what’s best for the group. If everyone does that, most of the group survives. If no one does, most of the group dies. That, in essence, is combat.”

The same men who brave gunfire to help each other in battle also think alike when responding to enemy tactics. When First Platoon members realize they’re in the maw of an L-shaped ambush—a killing zone—they position themselves where it will help the team. Somehow, the stress pushes soldiers into a highly effective mental state, and their loyalty to each other automatically makes them do whatever they can for everyone in their group.

“The idea that there are rules in warfare and that combatants kill each other according to basic concepts of fairness probably ended for good with the machine gun. […] Machine guns forced infantry to disperse, to camouflage themselves, and to fight in small independent units. All that promoted stealth over honor and squad loyalty over blind obedience.”

Mass killing machines obliterate enemy fighters, making any idea of nobility in battle pointless. It’s hard to salute your enemy from across the battlefield when all they want to do is slaughter you. Instead, modern military units search for ways to ambush their opponents and simply eliminate them.

“The machinery of war and the sound it makes and the urgency of its use and the consequences of almost everything about it are the most exciting things anyone engaged in war will ever know. […] War is supposed to feel bad because undeniably bad things happen in it, but for a nineteen-year-old at the working end of a .50 cal during a firefight that everyone comes out of okay, war is life multiplied by some number that no one has ever heard of. In some ways twenty minutes of combat is more life than you could scrape together in a lifetime of doing something else. Combat isn’t where you might die—though that does happen—it’s where you find out whether you get to keep on living. Don’t underestimate the power of that revelation. Don’t underestimate the things young men will wager in order to play that game one more time.”

Battle is where young men’s fantasies come to actual, vibrant life. Video war games can be loud and fast, but there’s no risk; a real chance of death is like an electric jolt that amps up emotions to screaming heights of intensity. When it’s over and soldiers think about it later, they know that only in battle will they ever get the full kick from those feelings. It’s part of what keeps them going, day to day, amid the constant tension of battle preparedness.

“I’m used to war being exciting and suddenly it’s not. Suddenly it seems weak and sad, a collective moral failure that has tricked me—tricked us all—into falling for the sheer drama of it. Young men in their terrible new roles with their terrible new machinery arrayed against equally strong young men on the other side of the valley, all dedicated to a kind of canceling out of each other until replacements arrive. Then it starts all over again. There’s so much human energy involved—so much courage, so much honor, so much blood—you could easily go a year here without questioning whether any of this needs to be happening in the first place. Nothing could convince this many people to work this hard at something that wasn’t necessary—right?—you’d catch yourself thinking.”

The sheer excitement of war blinds participants to the terrible destruction of it. No one wonders whether an ongoing, back-and-forth slaughter supplied continuously by replacements who, in turn, die, is worth it. These are young people who might otherwise make worthwhile contributions to their communities. It doesn’t matter that the game is destructive: It’s too exciting to forego.

“Soldiers themselves are reluctant to evaluate the costs of war (for some reason, the closer you are to combat the less inclined you are to question it), but someone must. That evaluation, ongoing and unadulterated by politics, may be the one thing a country absolutely owes the soldiers who defend its borders.”

Fifty men die in Korengal to advance the front by a single mile. It’s hard to evaluate that small achievement in terms of its value to the war effort, Afghan people, and American and world interests. The soldiers won’t judge it—instead, they’ll do everything in their power, including dying, to get the job done—so Americans back home must think of whether it’s worth the cost.

“Dirt collects in the creases of the skin and shows up as strange webs at the corners of the eyes and their lifelines run black and unmistakable across the palms of their hands. It’s a camp of homeless men or hunters who have not reckoned with a woman in months and long since abandoned the niceties. They belch and fart and blow their noses on their sleeves and wipe their mouths on their shirtfronts and pack every sentence with enough profanity to last most civilians a week. After the fighting ended last fall they got so bored that they started prying boulders out of the hillside and rolling them into the valley. They were trying to get one inside the wire at Firebase Phoenix just to keep Third Platoon on their toes. Caldwell finally told them to knock it off.”

Little fighting occurs during the winter months, and the men at Restrepo have nothing to do. There’s limited electricity and no running water; a shower is a distant dream. They abandon all pretense at being civilized, and boredom turns to mischief.

“I’ll tell anyone who will listen: I smoked a lot of weed, I sold a lot of drugs, I don’t care who knows it, it’s the way it was. I never got caught, my choice was pretty much on the streets dead, or in jail. I didn’t want either so I joined the Army. And now it’s dead or back home, but I guess the jail thing is out of the f**king equation. My mom raised me better than that, plain and simple. She just raised me better than to be selling drugs. She was the realest person in my life.”

Jones, the only Black in Second Platoon, is a realist who talks openly about his past and how he foresaw his own doom on the street. His choice of joining the army and facing lethal daily risks seems ironic, but he knows there’s a lot more honor and purpose in risking one’s life for a cause than doing it for cash and bling.

“No matter how many times you’ve heard it, you always turn toward the flight line when the 15s and 16s take off, a sound so thunderous and wrong that it would seem to be explainable only by some kind of apocalypse. Then the deltoid shape rising with obscene speed into the Afghan sky, its cold-blue afterburners cutting through the twilight like a welder’s torch.”

The massive power of American military weaponry can inspire or frighten, depending on one’s perspective. Fighter jets thunder out of Bagram Air Base with the sound of doom; though magnificent in flight, they can appear as fearful alien shapes that evoke images of science fiction overlords. This is good for instilling respect in the enemy, though it also evokes an eerie sense even among those who support the military effort: The campaign’s violence shrieks while its humanitarian efforts whisper.

“Religion gives a man enough courage to face the overwhelming, and there may have been so little religion at Restrepo because the men didn’t feel particularly overwhelmed. (Why appeal to God when you can call in Apaches?) […] The platoon was the faith, a greater cause that, if you focused on it entirely, made your fears go away. It was an anesthetic that left you aware of what was happening but strangely fatalistic about the outcome. As a soldier, the thing you were most scared of was failing your brothers when they needed you, and compared to that, dying was easy. Dying was over with. Cowardice lingered forever.”

Sustained warfare is a very unusual way of life; it requires more than the usual amount of confidence to withstand. The culture of a platoon, though thick with macho, is laced with an almost spiritual camaraderie. The danger, combined with the sturdy loyalty between the men, creates a unique brotherhood, in which life and death are regarded quite differently from the views of a civilian.

“Perfectly sane, good men have been drawn back to combat over and over again, and anyone interested in the idea of world peace would do well to know what they’re looking for. Not killing, necessarily—that couldn’t have been clearer in my mind—but the other side of the equation: protecting. The defense of the tribe is an insanely compelling idea, and once you’ve been exposed to it, there’s almost nothing else you’d rather do. The only reason anyone was alive at Restrepo—or at Aranas or at Ranch House or, later, at Wanat—was because every man up there was willing to die defending it.”

It’s not just that people are capable of bonding with others and risking their lives for them; it’s also that people want, even need, a group to protect. That desire is there before the bonding process; it’s ancient; it’s in our bones. In the modern age, high-tech weapons and a deep conflict with similarly bonded and loyal opponents can lead to mass slaughters. That’s not its purpose, but sometimes that’s the result.

“It’s a miraculous kind of antiparadise up here: heat and dust and tarantulas and flies and no women and no running water and no cooked food and nothing to do but kill and wait. It’s so hot that the men wander around in flip-flops and underwear, unshaved and foul.”

Waiting for battle is either dreadfully tense or extremely boring. A nice firefight would help the mood a lot. With few amenities and nothing to do but swelter, the men sink into a kind of fetid barbarism.

“[O’Byrne has] never had to get a job, find an apartment, or arrange a doctor’s appointment because the Army has always done those things for him. All he’s had to do is fight. And he’s good at it, so leading a patrol up [Hill] 1705 causes him less anxiety than, say, moving to Boston and finding an apartment and a job. He has little capacity for what civilians refer to as ‘life skills’; for him, life skills literally keep you alive. Those are far simpler and more compelling than the skills required at home.”

Nearly every soldier whose tour ends must deal with a dilemma: They don’t know how to be civilians. O’Byrne must decide whether to re-enlist and experience once more the fear, boredom, squalor, camaraderie, and ecstatic violence of combat or finally confront the terror of being alone in the world with few skills and no understanding of how to make ends meet.

“‘I prayed only once in Afghanistan,’ O’Byrne wrote me after it was all over. ‘It was when Restrepo got shot, and I prayed to god to let him live. But God, Allah, Jehovah, Zeus or whatever a person may call God wasn’t in that valley. Combat is the devil’s game. God wanted no part. That’s why our prayers weren’t answered: the only one listening was Satan.’”

O’Byrne knows that all he can depend on in battle is his team; everything else is just wishing and hoping. He also knows that, deep within the most vicious form of human activity, there lies the thing he loves doing the most. He’s well aware of the ethical dilemma of combat, and he has no better answers than anyone who has experienced warfare and tackled its imponderable contradictions.

“Bobby is running a fever of 103, coughing like a diesel engine and drinking all day long. Money marries a woman he met on leave a few months earlier. A soldier from Chosen Company gets taken to the hospital in an ambulance after collapsing in his room shrieking that people are trying to kill him. The toughest guys in the platoon find themselves crying every day, and the more vulnerable guys skirt the edge of sanity.”

The men of Second Platoon, waiting to muster out, already are struggling with the decompression from front-line duty to the blankness of a future without the platoon’s brotherhood. It’s hard enough to feel the eruption of emotions bottled up for months; it’s just as hard to adjust to a world where the sheer excitement of those stresses will be missing.

“O’Byrne refers to the base as ‘Coward’s Land,’ because it’s a place where guys who have never done anything but fill out paperwork can boss around guys who have actually fought for their country. A whole new set of rules apply that seem almost deliberately punitive of the traits that make for a good combat soldier.”

One terrible irony of war is that returning heroes get slammed up against a world that doesn’t know or understand what they’ve been through. Even as they try to process the emotional damage they’ve suffered, they’re required to deal with the petty concerns of people and places in peacetime that, to the returnees, suddenly feel pointless. It’s especially painful to submit to arrogant officials who have no idea what the soldiers have been through.

“The decision to leave the Korengal sparked a painful debate in the United States […] groups wanted to know why, if the Korengal was so important, we pulled out and—if it wasn’t important—why we stayed so damn long. In the press, the Korengal became emblematic of the entire war, a symbol of all the frustrations of fighting an insurgency in a far-off land. If we can’t even hold one small valley, people back home started asking, then what chance do we have in the country as a whole? And if we don’t stand a chance in the country as a whole, why don’t we just get out of Afghanistan now?”

The extreme difficulty of pacifying a country that has withstood invasions for hundreds of years hovers over the US operations in Afghanistan. Following the initial reprisals against Taliban and Al-Qaeda forces implicated in 9/11, the country's purpose became somewhat vague. This purposelessness plagues the American mission until finally, the US withdraws from Afghanistan entirely in 2021. The Taliban promptly retakes the entire country. The lesson, for the US, is a bitter pill to swallow.