I remember watching a documentary once about how US military intelligence studied the Normandy Landings in WW2. They were interested in it because up until that point the US hadn't performed a large scale invasion. They were curious to assess the performance in case they needed to order further invasions. What they observed horrified them - the majority of soldiers would shoot to provide covering fire so their unit could advance, but very few were shooting to kill, perhaps only 5% or so. They had no idea that the majority of ordinary American men aren't psychotic killers just looking for any opportunity to murder random people, they thought they would be desperate to do some killing, but here was their chance and typically they would try to avoid killing people unless it was necessary. This disturbed them greatly. So how do you turn the average man into a killer? A lot of study, work and refinement of coercive techniques has happened since the Normandy landings. If you've seen the film Full Metal Jacket you know it's mostly about the basic training process and how the military learnt how important it is to dehumanise soldiers, in order to install the killer instinct, or more specifically the temporary absence of moral qualms about killing. The developments in physiological manipulation of American soldiers have been very successful, I read that the average lethality of US marines during the invasion of Iraq had increased to the point where you would be hard pressed to find a marine that hadn't shot to kill. In fact I just found an article here that discusses the US militaries obsession with lethality - https://newrepublic.com/article/154970/james-mattis-lethality-buzzword-cult-military But what becomes of the ordinary men subjected to this sort of programming once the war is over? Especially JSOC operatives who were used like human drones, under the Obama program, to reduce collateral civilian damage by acting as assassin's. A new target every night, fly out, neutralise a target, fly back. Then do the same thing the next day, then the next, for six months straight. It's bloody tragic that so many servicemen are struggling with their mental health after going through those sort of experiences, being used like that, you can't just put it to the back of your mind. I don't think the US military will change it's mind on 'lethality', it's a numbers game, the argument that it's justifiable in the round is hard to argue. But it leaves these soldiers with a lifetime of reflection on the things they did and cognitive dissonance that is nearly impossible to reconcile with who they really are.