You can dispute the percentage Dill, but the phenomenon is beyond question.
Researchers at the site of The Battle of Little Big Horn (I think it was) found muzzle-loaders which had been reloaded many times but never fired. The soldier never ran but he could not fire on his countrymen either. If you think about it, the willingness to "butcher" would be the big difference between the Mongol, Hun, Roman and other barbaric hoards and their "more normal" victims.
The term "decimated" refers to the habit of Roman generals of killing every tenth (surviving) man of their legion if they lost a battle. A gentle reminder, so to speak!!
And on the high seas when sail dominated, why do you think there was so much rum on board a Royal Navy gunboat? Even hardened sailors needed "dutch courage" before their close encounters with "the enemy" (whoever they were at the time). Ever joined the Diggers for a gun-fire breakfast on ANZAC Day? Rum again.
Contemplate the changing face of warfare as the combatants could stand further apart and take the "personal" bit out of killing. That probably started with the big guns in The Great War and has escalated ever since... tanks, aircraft, missiles etc. But it still matters in an infantry engagement and I suggest that is a good place to start when examining some one sided battles in the last fifty years.
The Yanks have excelled here but the problem there is that they don't know how to switch from "combatant" to "peacekeeper". This failing lost them Vietnam and will cause them the same embarassment in Iraq.
The ability of our Oz troops to differentiate is what makes them such good peace-keepers.
