War

But once our ancestors escaped the eternal present by learning to speak, they could repeat stories that would make individuals accountable for their actions — or rewarded for them. That would create a strong incentive not to turn and flee while others fought off the enemy.

The glory heaped upon heroes in almost all societies might explain why young men are so eager to send themselves to war — or, if sent, to fight bravely. That would only work in a species that is capable of language, however; acts of bravery can’t follow a chimp home from the battlefield any more than acts of cowardice. Without language, courage just becomes suicidal foolishness.

Many such groups formed a tribe, and tribes either fought each other or formed confederacies against other tribes. The basic dichotomy of “us” versus “them” happened at the tribal level and was reinforced by differences in language and culture.

That bond is the core experience of combat and the only thing you can absolutely count on. The Army might screw you and your girlfriend might dump you and the enemy might kill you, but the shared commitment to safeguard one another’s lives is unnegotiable and only deepens with time. The willingness to die for another person is a form of love that even religions fail to inspire, and the experience of it changes a person profoundly.

Civilians balk at recognizing that one of the most traumatic things about combat is having to give it up. War is so obviously evil and wrong that the idea there could be anything good to it almost feels like a profanity. And yet throughout history, men like Mac and Rice and O’Byrne have come home to find themselves desperately missing what should have been the worst experience of their lives.

Public affairs will tell you that the Taliban are getting more brutal because they’re losing the war, but pretty much everyone else will tell you they started out brutal and aren’t losing shit.

The reason First Platoon did not get wiped out had nothing to do with the Apaches flying overhead or the 155s at Blessing; it was because the men reacted not as individuals but as a unit.

In some ways the anticipation feels worse than whatever may be waiting for them down in Yaka Chine or up on the Abas Ghar, and every man gets through it in his own quietly miserable way.

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.

One day Cortez got so bored that he ate a pack on purpose, hoping to bring on a firefight, but nothing happened.

Accidentally killing civilians is a sure way of losing the human terrain — this applies to both sides — and if you do that too many times, the locals will drive you out no matter how many hilltops you occupy.

Human terrain and physical terrain interact in such complex ways that commanders have a hard time calculating the effect of their actions more than a few moves out. You can dominate the physical terrain by putting an outpost in a village, but if the presence of foreign men means that local women can’t walk down certain paths to get to their fields in the morning, you have lost a small battle in the human terrain.

After a while we see lights moving on the slopes of the Abas Ghar, almost certainly Taliban fighters gathering up their wounded and dead. A soldier radios that in and suggests dropping artillery on them. Battalion is worried the lights might be shepherds up in the high pastures and denies the request.

It was as if every living thing in the valley, even the wildlife, wanted them gone.

The climb was so steep that the previous unit had installed fixed ropes on the bad parts. The Americans could make the climb in forty-five minutes, combat-light, and the Afghans could make it in half that.

By that standard, courage could be thought of as a uniquely human trait. Courage would make even more evolutionary sense if it were also followed by some kind of social reward, like access to resources or to females.

Considering the extreme nationalism of the Nazi era, one might expect that territorial ambition and a sense of racial superiority motivated most of the men on the German line. In fact, those concepts only helped men who were already part of a cohesive unit; for everyone else, such grand principles provided no motivation at all.

After the war, a pair of former American intelligence officers named Edward Shils and Morris Janowitz set about interviewing thousands of German prisoners to find out what had motivated them in the face of such odds. Their paper, “Cohesion and Disintegration in the Wehrmacht in World War II,” became a classic inquiry into why men fight.

And soldiers in World War I ran headlong into heavy machine-gun fire not because many of them cared about the larger politics of the war but because that’s what the man to the left and right of them was doing. The cause doesn’t have to be righteous and battle doesn’t have to be winnable; but over and over again throughout history, men have chosen to die in battle with their friends rather than to flee on their own and survive.

Dunbar then compared primate brains to human brains and used the differential to predict the ideal size for a group of humans. The number he came up with was 147.8 people. Rounded up to 150, it became known as the Dunbar number, and it happened to pop up everywhere. A survey of ethnographic data found that precontact hunter-gatherers around the world lived in shifting communities that ranged from 90 to 221 people, with an average of 148.