The U.S. Marines (and to a lesser extent other US infantry forces) are well-known for this sort of thing; for heavy mental preparation and priming to kill. It's

The U.S. Marines (and to a lesser extent other US infantry forces) are well-known for this sort of thing; for heavy mental preparation and priming to kill. It's standard in many other US forces, and non-US forces, to not experience this in training. As such, it's very possible to be in the US military without being trained to chant about killing people and so forth. What's more interesting is that this is not always known to people inside the group; that they believe it to be the standard (people from other military occupations are likewise often surprised when they witness a group of people team-chanting about killing people, having believed their own approach to be standard, and in my experience some European military find it a little disturbing, as they tend to be even further removed from this approach). Everyone takes their own experience and generalises it across the board; the US marines are an extremum in the field of mentally preparing (or indoctrinating) people to kill. Horses for courses; it only becomes a problem in the field when you put people heavily indoctrinated in killing into a deployment where not shooting people is really what's needed, and vice-versa. Unfortunately, that's where it has fallen down over the last decade or so.