We all have innate intelligence. We learn to listen to the environment because the universe speaks directly to us. As children we have both innate knowledge and the ability to 'listen' to the environment. If we touch something hot, we learn very directly not to do it again. That language is beyond conceptual learning. It is not privy to certain species. It is more primordial than speaking. For millions of years we have survived because our primordial intelligence demands that we avoid danger. We do our best. We see danger THAT way and so we will go THIS way.
You are a young man and have had a pretty good life ~ suburbs and lots of virtual danger on computers or televisions. Life is pretty soft and the future's looking pretty good. Suddenly you find yourself in an environment where real death is happening randomly all around you. Strangers speak a foreign language and you don't know whether the friendly ones will blow themselves up just to kill you - you are hated that much.
A bullet, a rocket propelled grenade, a bomb can snuff you out at any minute and it is happening to your comrades every day. The fear has become so overwhelming that you are shooting children, women, your
comrades, because you are beyond fear - you are in a state of hyper-fear.
Millions of years of primordial intelligence are screaming, "get to fuck out of here", and your humanness, your need for social acceptance is holding you in place. Deserters are not welcome in the family. But still, your primordial intelligence continues to scream. And as it screams small children scream with limbs blown off, mothers scream as they watch their babies die, babies that you and your comrades killed because you are in hyper-fear. And your friends are screaming at Afghans and Afghans are screaming at you. Everybody is screaming including the deepest depths of yourself. Even the weapons are screaming and they are all saying the same thing. 'Get to fuck out of here'.
If you make it back people will not understand you and you won't understand them. You are alienated from people that only experience virtual fear on video-games and war movies. Something deep, deep inside has moved.