ON CRUSADE (profanity alert):

When Uncle Sam met the Taliban: The remote Korengal Valley was one of the most dangerous postings in Afghanistan – before US forces pulled out last month, they experienced more than 40 fatalities. Sebastian Junger joined one of America's toughest units to find out what it means to feel the fear… and do it anyway (Sebastian Junger, 5/23/10, The Observer)

It soon became clear that if I were to get killed over the course of the next year, Restrepo – the most isolated base in the most hotly contested valley of the entire American sector – was almost certainly the place it would happen. It wasn't likely, but it was possible, so I had the strange experience of knowing the location of my fate in advance. That made Restrepo an easy focus for all my fears, a place where the unimaginable had to be considered in detail. Once, while leaning against some sandbags, I was surprised to feel some dirt fly into my face. It didn't make any sense until I heard the gunshots a second later. How close was that round? Six inches? A foot? When the implications of that kind of thing finally sink in you start studying the place a little more carefully: the crows that ride the thermals off the back side of the ridge, the holly oaks shot to pieces first by the Americans and then by the enemy, and the C-wire and the sandbags and shantytown hooches (soldiers' living quarters) clinging to the hillsides. It certainly isn't beautiful up there, but the fact that it might be the last place you'll ever see does give it a kind of glow.

For some reason my worry about dying took the form of planning the attack that would kill me – kill us all – in the most minute detail. Some of the men thought the place was impregnable, but I had other ideas. You'd want to hit Restrepo at four in the morning, I decided, while everyone was asleep or groggy from sleeping pills. (They take them to keep from jerking awake at night from imaginary gunfire.) First you'd hit the south-facing guard tower and take out the Mark 19, a belt-fed grenade machine gun that could stop almost any assault in its tracks. After that you'd rake the gun ports with small-arms fire from the south and west and send successive waves of men up the draw. The first wave would absorb the Claymore anti-personnel mines and the second probably wouldn't make it either, but by the third or fourth, you'd be inside the wire fighting hooch to hooch.

At night I put my vest and helmet at my feet and kept my boots tied loosely so that I could jam my feet into them but not trip over the laces. Arranging my things so that I could be out the door in 30 seconds was how I coped with those fears. It didn't work very well. I'd lie awake at night amazed by the idea that everything could change – could, in fact, end – at any moment. And even after I went to sleep those thoughts would just continue on as dreams, full-blown combat sequences that I wallowed through like a bad action movie. In those dreams the enemy was relentless and everywhere at once and I didn't have a chance.

As a civilian among soldiers I was aware that a failure of nerve by me could put other men at risk, and that idea was almost as mortifying as the very real dangers up there. The problem with fear, though, is that it isn't any one thing. Fear has a whole taxonomy – anxiety, dread, panic, foreboding – and you could be braced for one form and completely fall apart facing another. Before the firefights everyone got sort of edgy, glancing around with little half-smiles that seemed to say, "This is what we do – crazy, huh?" and those moments never really bothered me. I trusted the guys I was with and usually just concentrated on finding cover and getting the video camera ready. The fights themselves went by in a blur; if I remembered even half of what happened I was doing well. (I always watched the videotape afterward and was amazed by how much dropped out.) I truly froze only once when we got hit unexpectedly and very hard. I didn't have my body armour or camera near me – stupid, stupid – and endured 30 seconds of paralysed incomprehension until Tim darted through fire to grab our gear and drag it back behind a Hesco retaining wall.

Combat jammed so much adrenaline through your system that fear was rarely an issue; far more indicative of real courage was how you felt before the big operations, when the implications of losing your life really had a chance to sink in. My personal weakness wasn't fear so much as the anticipation of it. If I had any illusions about personal courage, they always dissolved in the days or hours before something big, dread accumulating in my blood like some kind of toxin until I felt too apathetic to even tie my boots properly. As far as I could tell, everyone up there got scared from time to time, there was no stigma to it as long as you didn't allow it to affect the others, and journalists were no exception. Once I got completely unnerved when Second Platoon was standing by as a quick-reaction force for Firebase Vegas, which was about to get attacked. This was my last trip, I was days from leaving the Korengal forever, and there was a chance that in the next few hours a Chinook would drop us off in the middle of a massive firefight on the Abas Ghar. I was getting my gear ready for the experience – extra water, extra batteries, take the side plates off my vest to save weight – but I guess my face betrayed more anxiety than I realised. "It's OK to be scared," Moreno said to me, loud enough for everyone else to hear, "you just don't want to show it…"

There are different kinds of strength, and containing fear may be the most profound, the one without which armies couldn't function and wars couldn't be fought (God forbid). There are big, tough guys in the army who are cowards and small, feral-looking dudes who will methodically take apart a SAW while rounds are slapping the rocks all around them. The more literal forms of strength, like carrying 70kg up a mountain, depend more obviously on the size of your muscles, but muscles only do what you tell them, so it still keeps coming back to the human spirit. Wars are fought with very heavy machinery that works best on top of the biggest hill in the area and used against men who are lower down. That, in a nutshell, is military tactics, and it means that an enormous amount of war-fighting simply consists of carrying heavy loads uphill.

I wore a body armour vest like the soldiers did – they called it an IBA – and a helmet, which they called a Kevlar. Together those weighed around 15kg. I had a 2kg video camera, 2kg of water in a CamelBak, and maybe another 8kg of food and clothing if we were going out overnight. I had my blood type, "O POS", written on my boots, helmet and vest, and I had my press pass buttoned into a trouser pocket along with a headlamp, a folding knife, and notebook and pens. Everything I needed was on me pretty much all the time.

Giving in to fear or exhaustion were the ways in which a soldier could fail his platoon, but there were ways a reporter could screw things up as well. Tim broke his ankle on a night operation on the Abas Ghar, but the medic told him it was only sprained so that, mentally, Tim would think he could walk on it. And he did. There was no other way to get him out of there, and if the platoon were still on the mountain at dawn they were going to get hammered. He walked all night on a fractured fibula with only Motrin as a painkiller, and they didn't tell him it was broken until he got to the KOP. They put a steel plate and a bunch of screws into his leg and a few months later he was back in business.

Several years earlier, in Zabul, I'd asked the battalion commander how discreet I had to be on my satellite phone, and he just said, "Big-boy rules, I hope I don't have to explain what that means." Tim was playing by big-boy rules up there, which essentially means making your interests secondary to those of the group no matter how much it costs you.

"There are guys in the platoon who straight up hate each other," I was told one morning by Battle Company's Brendan O'Byrne, who seemed to have a knack for putting words to the things that no one else wanted to talk about. We were sitting in ambush above the village of Bandeleek listening to mortars shriek over our heads, and there wasn't much to do but flinch and talk about the platoon. "But they would also die for each other. So you kind of have to ask, 'How much could I really hate the guy?'"