How armies turn kids into soldiers. From Gwynne Dyer's book War (excerpted here):
The way armies produce this sense of brotherhood in a peacetime environment is basic training: a feat of psychological manipulation on the grand scale which has been so consistently successful and so universal that we fail to notice it as remarkable.
The training, when it starts, seems impossibly demanding physically for most of the recruits - and then it gets harder week by week. There is a constant barrage of abuse and insults aimed at the recruits, with the deliberate purpose of breaking down their pride and so destroying their ability to resist the transformation of values and attitudes that the Corps intends them to undergo...The aim is to keep the training arduous but just within most of the recruits' capability to withstand. One of the most striking achievements of the drill instructors is to create and maintain the illusion that basic training is an extraordinary challenge, one that will set those who graduate apart from others, when in fact almost everyone can succeed.
...Nothing is quite so effective in building up a group's morale and solidarity, though, as a steady diet of small triumphs. Quite early in basic training, the recruits begin to do things that seem, at first sight, quite dangerous: descend by ropes from fifty-foot towers, cross yawning gaps hand-over-hand on high wires (known as the Slide for Life, of course), and the like. The common denominator is that these activities are daunting but not really, dangerous: the ropes will prevent anyone from falling to his death off the rappelling tower, and there is a pond of just the right depth - deep enough to cushion a falling man, but not deep enough that he is likely to drown - under the Slide for Life. The goal is not to kill recruits, but to build up their confidence as individuals and as a group by allowing them to overcome apparently frightening obstacles.
...But there is nothing in all this (except the weapons drill) that would not be found in the training camp of a professional football team.
I remember reading once about the relaxed training fitness standards for female military recruits, and being upset at how progressive social engineers were ruining the US military as a fighting force. I'm sure many in the military felt the same way, but we all of us were buying into the mythology described above. What matters for recruits is that the challenges are superable, not that they turn out a person of a certain physical caliber. For how many active military train and condition so fanatically once their basic training is done? Surely not so many? It's the tone of their brains, not necessarily their muscles, that makes them capable soldiers.
Even more true nowadays, where war is fought more and more by joystick and remote than sticking knives in people. The only question for female soldiers is whether they are willing to do as they are told and kill whom they are told.