[Spearchucker]

"...being on the ground with a gun makes you more likely and less inhibited..."

It's actually the exact opposite. Seeing the person you're about to kill makes it harder to pull the trigger (given a normal psychology, for whatever that's worth). If you're interested, the book linked to below goes into great detail about this.

http://www.amazon.co.uk/gp/aw/d/0316040932/

[CHY872]

Yes, but historically armies have proved more than adept at drilling those instincts out of people.