For the best part of a year, in 2007–8, the writer and reporter Sebastian Junger and the photographer and filmmaker Tim Hetherington visited and revisited the Korengal Valley in eastern Afghanistan. They were ‘embedded’ with Second Platoon, Battle Company, ‘The Rock’ Battalion, 503rd Infantry Regiment, 173rd Airborne Brigade Combat Team, first of all in the forward operating base known as the Korengal Outpost (the KOP), and then in an outpost of the outpost, as far out on a limb as it is possible to get, witnessing the kind of war that would not have seemed completely foreign to Xenophon or Herodotus, give or take a whiff of grapeshot, or the smell of napalm in the morning.

Battle Company are real soldiers. ‘Combat infantry carry the most, eat the worst, die the fastest, sleep the least, and have the most to fear,’ reports Junger in his account of the experience. ‘But they're the real soldiers, the only ones conducting what can be considered “war” in the most classical sense, and everyone knows it. I once asked someone in Second Platoon why frontline grunts aren't more admired.’

For these soldiers, the Korengal is a good approximation of hell on earth. In winter, bitter cold, so cold that they wear balaclavas under their helmets. In summer, a hundred degrees every day, crawling with tarantulas, infested with fleas. At night, the wolves begin to howl; mountain lions creep through the KOP looking for something to eat. Colonies of monkeys invest the place, setting up a fearful screeching. There is a bird that sounds uncannily like an incoming rocket-propelled grenade; the men call it the RPG bird and flinch whenever they hear it. At the outpost there is no running water, no electricity, no hot food, no alcohol, no drugs, no communication with the outside world – no life, one of the soldiers explains, ‘like being a monk in, like, Tibet’.