Troopers

Matt has a good post about the effects of militray training. He's already simplifying a complex book in the post, but here's a sample, though you should go and read the whole thing (there are some interesting points in the comments as well):

Essentially there's a strong, inbuilt barrier against killing other human beings. Originally, basic training for conscript armies consisted of how to shoot the gun, lots of marching, and obey this guy. The main point of all the drills is to get you to obey the officer. Hard physical exercise, lack of sleep, reduces your inhibitions, lots of drilling in formation, all encourages you to obey orders and do what everyone else does. This was somewhat effective at getting people to break their inbuilt resistance to killing people, but not very. Modern basic training involves getting someone in a much more realistic setting, e.g. sitting in a foxhole using live ammo to , and offering rewards, such as time off if you shoot enough of them, The point being that it's much, much closer to real combat.

Now this is good for fighting wars -- having 70% more of your soldiers doing what they are paid to do obviously makes you a better fighting force. However it also means that you have 70% more of your soldiers prepared to do something normally they would not do, and as in this case it's killing someone, this does not make soldiers very good peace-keepers. It also makes such reports as we have heard recently almost inevitable.